Winchester Disks – All You Need To Know

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More and more business microcomputers now offer a Winchester disk drive as an option or add-on. What difference do these devices make, and are they worth the extra money? Will your software still be compatible? Claire Gooding takes a user’s view.

The name ‘Winchester’ for most people in the computer industry conjures up not a cathedral city in Hampshire but a disk for storing masses of data.

The first generation of microcomputers has accustomed most users to floppy disks: not an ideal medium because of their vulnerability (not to be handled after eating fish and chips!) and the limits on the amounts of data they can hold. The size and capacity of floppy disks has increased enormously since the first versions became common in the mid-seventies, but for many users the capacity of even the largest floppy disks cannot cope with their needs.

People quickly became acquainted with the drawbacks of floppies: their tendency to run out of space, and worse, to announce ‘DISK ERROR’ at the slightest excuse. Serious business use of microcomputers made it essential to provide a more robust and efficient form of mass storage.

The first to produce a form of hard-disk storage were pioneers who were prepared to rig up custom-built hardware and write the necessary software to store and retrieve data – usually in the lowest possible form of language, machine code. Although software houses (who really needed more storage space) could probably cope with such demands, the average end user needed something off-the-peg.

By 1980 Winchester disk technology had moved far enough to provide 8” Winchester disks for micros, although they were highly unreliable. One manufacturer who supplied these 8” disks as an optional add-on to his microcomputer recalled that “at any one time we could be fairly sure that only half of the disks we supplied were actually working – the rest were either winging their way to us or back again after repairs!

Reliable solutions

As always, it didn’t take long for the technology to advance to the degree that within only a couple of years there were far more reliable solutions in Winchester form.

The users who clamoured for mass storage first were those who bad bought Apples and PETs (Commodore) in the first wave of microcomputing. At the time few had envisaged that the PET would become one of the most widespread business tools of its time, but its popularity – and the fact that it ran out of space very quickly – meant that Commodore had to do something.

The solution was the Shark disk, made by Mator. The people who had invested in PETs were resourceful and adventurous on the whole, but couldn’t really be expected to muck about with software – especially machine code – to get their programs to on on the hard disk.

“When Mator was approached with the idea of matching the PET with a hard disk, one of the prime requisites was that it should look like one of the existing drives,” explained David Briggs, Hardware Sales Manager, for Commodore. “That way there would be the absolute minimum of software compatibility problems – if it works on the standard floppy, then it should work with the hard disk.”

Meantime, Apple had found its own solution. First the Corvus hard disk came on the scene, then Apple followed with its own Profile.

Other suppliers developed Winchester bolt-ons for the many Z80-based machines. The only problem which such ‘afterthought’ bolt-ons might encounter was that most of the systems they were bolted to had never expected to talk to a Winchester. So unless the user was prepared to write his own Input-Output routines in machine language, he had to make sure that the manufacturer who supplied the disk also supplied a version of CP/M or whatever operating system was concerned, with the necessary BIOS (Basic Input Output System).

BIOS

The BIOS is a piece of software which allows the operating system to link with specific peripheral devices like disk drives and printers. It would be a pretty silly supplier who didn’t ensure that customers could use his wares, so the BIOS problem is not a great factor – you’ll find someone who can offer you a hard disk option among the many independent suppliers of bolt-on Winchesters which have sprung up in the last two years.

On the whole, moving to a Winchester shouldn’t demand any alteration in your applications programs, the exception being if you have bought a system where the protection built into the programs as a bar to illegal copying, is connected with the physical disk – as in the Silicon Office from the Bristol Software Factory.

It didn’t take long for the other manufacturers to realise that their systems would have an edge on competitors in the market place if they could offer Winchester disks as an option, so that buyers could later expand, even if they couldn’t afford mass storage to start with. By 1981 such configurations were common.

By 1982, not only was the hard disk option common, but manufacturers were striving to improve the service they gave. Not all the space on a Winchester is used up, partly because some sectors are always kept spare, ‘just in case’. Better organisation of data, so that operations are optimised, can mean an improvement on access times and throughput.

NEC offers such an ‘improved’ Winchester with its PC 8000, called DisCache. “What DisCache does is to keep the most commonly accessed pieces of data in a RAM buffer,” explained Marketing Manager for the PC, Alan West. “With this technique the most frequently used bits of data are likely to be in the RAM buffer, so there’s no disk access needed at all.” West describes DisCache as “the most intelligent implementation of a Winchester” because it also deals with the eternal problem of backup.

“DisCache keeps a note of the sectors to which data was written, for example, daily. So that at the end of the day, it’s only a matter of backing up that data, using only part of a floppy. With our system, backup becomes a simple end-of-day/month procedure. There’s a complete management system for recovery, so that it becomes a simple serialised restoration of data: it never needs more than twenty diskettes.”

Backup

Backup is one of the hidden costs of buying a Winchester disk. A complete backup needs as many diskettes as two dozen in some cases, and can be extremely tedious: prohibitively so if there’s a need to make a complete backup every day. The alternative is a tape streamer, which can be pricey.

Just as frustrating, is the rare occurrence of re-formatting when there is a disk problem on the Winchester. “First of all,” said one user, “you have to find the re-format program which you threw off the disk to make space months ago. It’s then that you discover that the re-format – if you find it – is a pig to use with lousy documentation. Of course, it’s so seldom used that you only discover this in real emergencies.”

Nevertheless Winchesters have lots of hidden advantages, too. One of the busiest development areas these days is in operating systems, and manufacturers are looking beyond multi-user systems to networking. Compared to the home computer user with his cassette or floppy, this is computing on a grand scale and couldn’t be envisaged without some form of fast storage and retrieval.

Newer operating systems – especially time-sharing systems like the up-and-coming Unix, tend to assume that their targets run on Winchesters.

Having more storage should also have an impact on the people who are doing the actual development of software applications. Being able to hold data together all on one disk has repercussions on the ‘integration’ of software. Eventually we should see more sophisticated systems which perform automatic updates, or create one-off reports with data from many different files. Relational databases – notoriously power-hungry and greedy for space – become another possibility, and that means that users should be able to make any combination of data items, or delate them, to make the kind of selective enquiry which most present systems are not flexible enough to allow.

Winchesters have already played a vital role in making software development easier, and it’s likely that they will even lead to an improvement in the quality of software… or that’s the theory, anyway.

What is it?

For those with an insatiable appetite for technical explanations, here’s a quick look at how a Winchester drive works.

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A Winchester disk drive is hermetically (airtight) sealed to keep out dust and grime. The recording head ‘flies’ just over the surface of the disk drive on a cushion of air.

The main thing that you need to know about Winchester disks is that they are larger – usually 5 to 10 times the capacity – than the floppies which have been the staple storage medium for most microcomputer users.

The main difference between floppies and Winchesters is that Winchesters are made of hard metallic material – hence the term ‘hard disks’, whereas floppies are just that – if you extract one from its cardboard shield you’ll see something like those flimsy disks that used to be given away with magazines as advertising gimmicks.

The advanced technology used to create Winchester disks not only allows far more data to be packed onto a smaller space, but results in what should be a less troublesome medium than floppies. This is due to the fact that Winchesters are sealed in an airtight casing so that they operate in an immaculately clean environment. This means that the hard disk (in the raw it looks much like a brown LP) doesn’t deteriorate as fast as a floppy disk because it is not subjected to the same sort of wear and tear, caused by dust particles and other abrasive matter. The pros and cons of putting all your precious data on to a Winchester disk are tied closely to that ‘hard’ medium.

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Unlike a floppy disk unit, a Winchester frequently shows nothing on the exterior. Despite this, the level of noise is surprising high.

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Tape ‘streamer’ cartridges are probably the best form of back-up to a Winchester disk, though most people use a floppy drive for reasons of economy.

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New half-height Winchesters can be expected to appear on new microcomputers in a few month’s time.

IBM first developed the technology, and stories abound as to how it came by the name Winchester. Sorry, Anglophiles, but most sources, including IBM, seem to agree that it wasn’t named after a quaint Hampshire city: not directly, anyway. The engineers of IBM’s development team named it after the Winchester rifle because the prototype disk drive supported two disks of 8 megabyte capacity – 6:6. The name stuck.

IBM’s aim was to build an exchangeable disk pack with a very high data density. Previous attempts failed because the task of making the read-write head accurate enough to find the right track was almost impossible when the disk itself had to be exchangeable. The read-write head, which picks up data from the disk, had to be able to find the right track within thousands of an inch. Even if this were possible, the whole arrangement would go out of line as soon as the room temperature changed, because of thermal expansion.

Cushion of Air

IBM solved the problem by doing away with the disk-head alignment altogether. The head assembly became exchangeable, along with the disk. The sensor, which in older technology used to be part of the head assembly, was replaced with information held on the disk itself, and the head ‘flies’ across the disk on a thin cushion of air. The head must never actually touch the disk, which is travelling at about 100 mph – quite fast enough to cause a ‘crash’ which would damage the head and wipe out data.

The aluminium surface of a Winchester disk can be machined flat to a tolerance of around ten millionths of an inch, and the head flies about twenty millionths of an inch above the disk surface: about a hundredth of the diameter of a human hair.

The thinner the cushion of air on which the head flies, the more data can be crammed onto the disk, in greater density. The problems are that flying as close as twenty millionths of an inch, the head stands a fair chance of encountering an almighty piece of dust, or a mountainous flake of cigarette ash. The solution: assemble the whole thing in a ‘clean room’ atmosphere, then seal it for life.

The Winchester’s light low-flying head lands as gracefully as Concorde on the disk’s surface only when the disk is turned off and slows to a halt. As a result Winchester heads don’t need the expensive and unreliable mechanism, (rather like the needle on an automatic record-player) which on older-design hard disks was needed to lift and retract the head before the disk stopped.

So the development of the Winchester opened up possibilities of storing vast amounts of data in fairly robust conditions. It’s hardly surprising, given the technology involved, that the Winchester disk was expensive. But it didn’t take long for IBM’s competitors to get on the trail, and prices dropped as the technology improved.

Practical Use

The first disks were 14” – too large to be of any practical use to microcomputer users. But once the teething problems were over, Winchesters began to look like a very attractive alternative to diskettes. Storage rates of 5, 10 or 20 megabytes began to appear in much  smaller packages. By the end of 1980 8” drives which took up no more space than a standard floppy drive were becoming available in reasonable quantities. The price was relatively high, but the speed and capacity were ten times better than a floppy disk.

As the technology improves, the price is dropping as manufacturers make mechanisms simpler, and capacities have crept up from 40 to 80, and now even 450 megabytes.

The other thing that has changed drastically is the size. Winchester disks now come in even smaller sizes than the 8” drives. The next revolutionary step was the 5” or 5.25” disk drive, pioneered by Seagate, and now the 3.25” disk drives are making their appearance, heralded by Syquist’s prototype, which drew the crowds at the National Computer Conference in the USA in 1982.

Who needs one?

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Until recently, Winchesters were only available as add-ons from third-party suppliers (this Corvus unit is one of the most popular). Now more manufacturers will be offering their own.

Not everybody needs a Winchester disk – but if you have a large database or want an integrated accounts system then a Winchester should be high on your shopping list.

Who needs a Winchester? When you find yourself surrounded by a sea of floppies, when your accounting programs can’t be run without switching and swopping, and when your operating system is forever hung up looking for spare sectors, then perhaps it’s time you considered a Winchester.

It’s the sheer lack of space which drives most users to consider hard disk storage, that, and the fact that having their data on a Winchester gives them a nice warm feeling of safety. The sealed disk appears much less vulnerable than a series of small floppies, which can get bent, have cups of coffee spilt on them, and can very often suffer from disk errors. The business of backing up at the end of the day is also so tedious that many people simply get lazy about it, and come to grief when their floppies pack up.

The other factor that pushes some users to the decision of spending a lot of money on a Winchester disk drive is speed. This can become a crucial factor with a micro which is being used for several different applications in a business environment. Not only does the actual disk access take much longer on floppies, but operators can take an inordinate amount of time shuffling data around to squeeze things in.

If there is some question of implementing a multi-user system then a Winchester comes higher up the list of priorities. Not only is speed more crucial in a multi-user environment, but the volume of data and programs is likely to be so great that the system couldn’t work efficiently without a Winchester.

Database

The other software acquisition which demands a certain amount of hardware investment is a database. The pros and cons of running one’s business on a database are still debated up and down the land in mainframe installations, but for users who are considering a set of applications depending on one set of data, it’s a solution worth consideration.

There are several microcomputer databases (Logica’s Rapport, Pactel’s MDBS) but the use of any of them – or even the data files created to run, say, a stock system, can take up a great deal of space. Depending on the access method used and the number of data items, a large set of files can slow operations down considerably. “All I can say about anyone who tries to run a database off a floppy,” said one user, “is that they must be very, very, patient.”

Nevertheless the collection of your data and its organisation into a database can have some valuable spin-offs, especially to a business user. It opens up the possibility of ‘integrating’ operations. This means that instead of executing each task independently and perhaps only updating one file, updates which have a bearing on one set of data – for example the stock file and the supplier file – can be automatically posted. When creating a report, data from several different areas can be called on, and individual programs can all tap the same data.

There are great advantages in this approach, since expanding operations (perhaps adding a payroll) can use information that is already filed. A business user who wants to make the most of the great amount of information stored in his files can also think about such applications as modelling and forecasting; again, a very space-hungry sort of operation because of the mathematical formulae used to manipulate large amounts of data.

Program Generators

Most of the space needed to run integrated applications, or a database system, is taken up by the tables and pointers which have to be set up as a sort of index to link the various pieces of related data. The more links there are, the more space is needed for the tables.

The other way of creating applications which link together is to use a sophisticated applications generator. These have become very popular in the last couple of years, with products like the Last One, and Personal Pearl becoming almost household names. These can be very effective, but nearly all of them work on the same principle: menus which lead the user through the business of setting up a database, linking data and setting up ‘keys’ on which data is sorted (e.g. customer number or surname), and then actually creating the application.

In this case, not only do you need space for the files you create and the tables and indices that they use, but even more space for the heavy business of generating code. Code, which is generated rather than hand-written, tends to be less efficient because it has to be ‘ready-made’, and it will often take up more space and work more slowly than custom-built programs. If you are planning to use an applications generator then a Winchester disk may well be a necessity, since it is easy to run out of space on floppies when creating only one small system.

Software houses tend to go for mass storage of some sort for the obvious reason that they have far more to store, and will often keep several ‘development’ versions of one program, plus sets of test data.

If you have an accounting system or stock system which has been written specifically to run on a pair of floppy disks, then you should be able to manage quite well without hard disk storage. However, transferring the system to a Winchester will make a difference in speed and efficiency, though it probably isn’t worth the effort unless you plan to expand in some other way.

First published in Microcomputer Printout magazine, April 1983

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Apple Lisa

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Each month one of Microcomputer Printout’s team of experts gives a vast amount of free publicity to a product they happen to like. Julian Allason opted for Apple’s new LISA – because, quite simply, it works the way you do.

Soft Soap

Julian Allason is critical of LISA’s Software.

“A soft answer turneth away wrath” says the Bible’s book of Proverbs. And answers to the microcomputer problem come no softer than LISA. Indeed, so friendly is she that the doyen of micro dealers, Mike Sterland, professed himself worried that existing Apple clients might be jealous at the thought of mere newcomers enjoying her sundry charms.

There can be little double that what I suppose we must call the LISA operating system – although it is so transparent as to be invisible – is superbly executed. After a few minutes one is merrily scuttling the mouse across the table top; selecting here; opening there; consigning files to the waste basket, and drawing the prettiest of pictures. To the experienced hacker, the sheer joy of being able to see what files are open; what jobs remain to be done; whose birthday is impending; is little short of a revelation. Beginners soon take it for granted – which is perhaps the highest accolade of all.

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The movable mouse with its single ‘select’ button is used to point to a function on the screen

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But is the applications software (although again this is a term Apple wouldn’t dream of using) as good? I fear not.

Like the curate’s egg, it is good in parts. The authoritative Rosen Electronics Letter, describes them, with the exception of LISADrawer and LISAProject as ‘pedestrian versions of standard functions that have been better done elsewhere’. Quite so. The point, however, is the degree of integration between them. Unhappily, even this is not as comprehensive as it might have been. The LISAWrite word processor for example does not allow you to insert information from the other applications, except by adding an extra page to the document you are working from.

If you are the sort of writer who needs fancy functions like footnote management and indexing, you would be frankly better off with Wordstar (and it is just a matter of time before that appears on LISA). On the other hand LISAWrite gives you lots of type faces and sizes to play with. And you can print them all out exactly as they appear on the screen, using both Apple’s new dot matrix printer, and, amazingly, the daisywheel printer. Most of the usual functions for manipulating text are there, and in my humble judgement, the program is more than adequate.

Much the same judgement must apply to LISACalc, which would be a fairly run-of-the-mill first generation spreadsheet if it didn’t offer variable column widths and one or two other goodies. One criticism levelled at it is the absence of multi-sheet consolidation, a feature which might have been expected to appeal to the corporate users who supposedly constitute LISA’s target market.

LISAGraph offers the usual types of business graphs in four different sizes. Thanks to the 720×364 dot resolution of the 12” screen, they look a lot better than on most other micros. Up to seven different sets of data can be held, and converted into graphic form.

This data can either be keyed in directly as a set of values, or moused over from the Calc program. The point that caught the eye of almost all lucky enough to have had a sneak preview of the system, was the way in which the graphs change automatically following any amendment to the data. Clever stuff!

LISA Terminal is optional, and it sounds like, and emulates DEC VT100 and VT52 modem and terminals. IBM 3270 emulation is likely to be included by the time LISA goes on sale here sometime this summer (is September still the summer? “It’s real hot out here in September,” says my chum in Cupertino with a wink).

And now the exciting bits. LISADraw is astonishing. If you’re drunk it will even straighten out your lines. Combine it with LISAGraph or LISAProject and the results get to look very professional indeed. The first time I saw LISA the demonstrator, Apple’s Brian Reynolds, created first one, then a whole series of drawings of LISA just by selecting from lines, shapes and shading with the mouse. And, Apple II users please note, text can go anywhere on the screen.

LISAProject is for critical path analysts. I’m no expert on project management, but even I could understand the schedules when they were displayed in graphical form, showing the critical paths amongst tasks, represented by boxes containing the details of the resources required, and milestones. In true calc fashion the critical path can be changed to take into account changes in resources – more Irishmen hired, a compressor stolen, for example – or unexpected delays. Once the output has been tarted up using LISADraw, the results are well up to management consultancy standards.

The last application is LISAList which is really a sort of database for dumbos. I’m not sure why it’s been billed as a list management package as several of the more standard mailing list functions seem to be missing; ditto a proper report generator.

Apple would probably argue that LISAList is intended for general use rather than high powered mailing or database management. Packages dedicated to precisely these applications may be expected sometime in the future. Quite when, however, remains a bit of a mystery. As I write, more than a month after the launch, the LISA development toolkit has yet to appear, and latest word is that it is unlikely to be before June. Without it third party software houses are going to have difficulty writing any applications programs that exploit LISA’s true capabilities. Without those programs LISA could turn into a seven month wonder.

The computer supports Pascal, BASIC, and COBOL languages so the problems are hardly insoluble. The onus must also be on Apple to get out and sell LISA in quantity. These self-same software houses subscribe to a strictly commercial code. Commandment 1 of this states that Thou Shalt Only Convert Software for Machines with a Large User Base’.

So different and so special is LISA it can truly be said to have a user base of zero.

But perhaps not for long. I, for one, have placed my order.

Lisa – An Expensive Lady?

In counterpoint to the otherwise noisy proceedings at LISA’s launch was the silence that greeted the announcement of the price – the sterling equivalent of $10,000 plus travelling expenses.

With the pound sick, and the gnomes tremulous, that translates to something like £7,500 – a lot of anyone’s money for what is still essentially a personal computer. Have Apple blown LISA’s chances then?

Some of the more cynical dealers thought not. “No one knows better what the market will bear than Keith Hall,” remarked one computer retailer, who had known the rugger-playing Sales Director in his incarnation as Commodore’s marketing mafioso. The existence of a market at that sort of price level is certainly not in doubt. Xerox have demonstrated that by selling every 8010 work station – the only piece of hardware remotely comparable to LISA – at over £11,000 each.

The other conclusion reached by the trade, after the customary head scratching, was that when LISA does arrive it could be in short supply. Indeed Apple have already indicated their intention of restricting LISA dealerships to a select few. The official explanation is that only the most experienced business systems houses would be able to do justice to the new baby. Quite how this squares with Apple’s claim (probably justifiable) that LISA is so easy to use that it can be learned in twenty minutes, is anyone’s guess.

Rumour, that oft ill-informed lady, has it that the original UK target price was £6,500; that was before the gnomes weighed in and sterling tumbled. There seems also to have been genuine disagreement on price within Apple. Sources close to the company’s Cupertino headquarters talk of two distinct schools of thought, one favouring a ’low’ price around the $8,000 mark with a view to maximising the company’s advantage in being first. A second group is said to have canvassed a $12,000 price tag on the basis that this would generate the optimum revenue, given the inevitable supply problems during the first year.

In the event, Apple’s chief executive, Mike Markkula, seemed to have split the difference, conscious perhaps that LISA’s market lead had been whittled down by successive software delays.

The unknown factor in the LISA price equation is Macintosh, LISA’s little brother. The conundrum now entertaining Cupertino’s corporate types is this: how cheaply can we make Little Mac?

Like LISA Macintosh is based on the Motorola 68000 16-bit microprocessor. Like LISA it should run much the same software. But will it? Like Topsy, LISA’s software just grew and grew and now occupies more than two megabytes of memory in all. Any possibility of marketing a floppy only version of LISA went out of the window more than a year ago; hence the presence of the separately boxed Profile five megabyte hard disk. Exactly the same problem now arises with Little Mac.

One theory now current amongst Apple watchers proposes $10,000 as an artificially high price for LISA, simply in order to maintain market separation from Macintosh. All this speculation – for speculation it largely is – is based on the assumption that LISA is overpriced. But is it? Try as one may, it is hard to put together a 68000-based system with Hi Res graphics, a megabyte of RAM, five megabytes of Winchester storage and half a dozen or so applications packages and still find oneself with much change from £8,000. And what price user friendliness?

LISA may not be within reach of everyone’s pocket, but it certainly looks like good value to me.

Which side of the Blanket?

Julian Allason examines Lisa’s parentage…

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The Xerox Star was the first workstation to employ the multiple-window technique. More recently Visicorp announced Vision for the IBM PC.

Frowns outweighed smiles as microcomputer folk reacted to the launch of Apple’s LISA computer last month.

The most maniacal grin adorned the visage of Apple’s rugger playing Marketing Director, Keith Hall, as he exhorted his dealers into orgasms of excitement at the prospect of selling the wonder micro.

The details of LISA, which will not have come as a very great surprise to readers of this organ, brought a furrow to the brows of competitors. “Now everyone will want integrated software,” moaned one small British microcomputer manufacturer. “Look how long that took Apple to develop – and we don’t have a fraction of their resources.”

Ecstasy was also less than unanimous amongst dealers. “Apple have wrecked the market. I’ve already had two of my best customers call to put a freeze on further orders. The worst part is that Apple won’t even be able to deliver LISAs for six months and then not in any quantity,” complained one member of the Computer Retailers’ Association.

Wry smiles were the order of the day in Uxbridge, headquarters of Xerox, makers of LISAs only competitor, the 8010 workstation, otherwise known as the Star. As noted elsewhere on these pages, LISA owes much of its heritage to work done at Xerox’s Palo Alto Research Center. Work that culminated in the Alto prototype user friendly computer. From the Alto – so far the only personal computer to have achieved true cult status – sprang from the aforementioned Star.

When industry pundits take a step back from the trees to inspect the wood, they will notice something very odd. Working from the same starting point, Apple reached a very different – one is tempted to say the opposite – conclusion from Xerox. For the Star is viewed by Xerox as a workstation for their Ethernet local area network. Apple, on the other hand, are adamant that LISA is a one-man machine, a personal computer that will adorn the desk of professional managers.

It is a curious conflict and one is tempted to wonder whether both companies can be right.

In truth not even Apple are convinced that they enjoy a monopoly of wisdom. As one senior manager remarked, after looking round to ensure that we were not being overhead, “In scientific circles the very best rows start with opposing conclusions being drawn from the same data…”

But it may not even be a two sided argument, because VisiCorp, whose VisiON operating environment has received the rough edge of Apple’s corporate tongue, think they are dealing with a very different sort of animal. If one could reconstruct the chain of evolution of the concepts first developed at Xerox PARC and Stanford University, it might go something like this: Alto user friendly personal computer becomes the Star workstation, a single component in a network of stations sharing printing and file storage resources, but its principal function is to exchange information.

As a personal computer company, Apple find other aspects of the Alto more sympathetic. The use of multiple screen windows, the mouse as a pointer to them, and of icons (small graphic symbols) to indicate the status of the work in hand all appeal. The network emphasis less so. Apple see the integration of the most popular office applications as a means of closing the gap between computers and office functions as they are normally (i.e. manually) carried out.

At the bottom of the chain, or at least as far down as we can see for the nonce, is VisiCorp. In their world view the PARC concept is primarily a means of making applications programs more user friendly. Not surprisingly, the first programs to receive the VisiON treatment will be VisiCalc, VisiWord, VisiPlot, VisiTrend, Visi etc. And least anyone deprecate that, your correspondent would like to add that he was enormously impressed the first time he sat down with VisiON. Moreover, the system has received the imprimatur of mega-mini-computer-maker Digital Equipment Corporation. In the computer world this is the equivalent of not just a feather in the cap for VisiCorp, but a whole bird in their bonnet.

Whether future micro biological expeditions down this particular evolutionary train will be warranted in the future remains to be seen. Certainly there are some interesting growths under culture in the labs of Microsoft and Digital Research. Our microscopes will be trained in their direction over the coming months…

First published in Microcomputer Printout magazine, April 1983

Filing the Fillings

Fillings

Michael H Rich describes how micros can improve dental health

Using any kind of computer in a dental practice neatly divides itself into two compartments: use in the office, which is comparable to using a micro in any small business, and use for clinical records. This latter use involves a far wider concept than ‘ordinary’ business use as the software is highly specialised and, as will be described below, needs the use of combined graphics and text on the screen to be fully effective.

Before the advent of the microcomputer there was very little hard/software available for the dentist to be able to introduce computerisation into a dental practice.

What there was was in the nature of a large ‘mini’, complete with the necessity for an air-conditioned ‘cubicle’ for the CPU which used fixed/removable hard disk cartridges. This, of course, allowed a multiuser facility but in the context of a small dental practice was far too expensive to be cost-effective.

Minicomputers are still available for dental practices; they are smaller in size as well as being slightly cheaper in price, and the suites of software with these systems do a reasonable job of helping the dentist to run his practice. The argument about being cost-effective still applies and thus they are for the larger practice only.

The micros of the Apple/PET/Tandy variety (and this list is by no means exhaustive) have, of course, opened up the world of computerisation for the small business, and it should be realised that a dental practice is precisely that. Many of the available software packages for running such a business can be applied to a dental practice. The management of accounts can be dealt with in a standard manner, as can stock control; although a practice employing half a dozen people hardly needs payroll software!

What distinguishes the dental practice from a small business is the clinical aspect of treating patients and the paperwork that this generates. When examining patients a dentist records the clinical information derived from the teeth in a form consisting of various shapes to designate types of cavity, fillings present, teeth to be extracted, dentures present and a variety of other conditions. This pictorial representation of a mouth is easy to scan and assess and is an internationally standard method. To record this information in written form, although suitable for a standard database software package using routine file handling procedures, would be very long-winded and would mean abandoning the standard procedures used.

There is software available for use on micros which does do this graphic charting of the clinical conditions in a mouth and this is allied with space to write clinical notes of treatment to be done, or which has been done. This is often conjoined with a suite of programs which will price the work done, whether under the NHS or privately, and will produce bills for patients and carry out the usual reconciliation with payments, aged debt analysis and so on. The software will often include a facility for routine recall of patients at a standard time interval and this raises the other major aspect of the application of computerisation of a dental practice – the appointment book.

It is necessary to realise that anything other than the appointment book in a dental practice is capable of being replaced or renewed in the event of a complete disaster, eg, a fire. To take an extreme example, if the premises are totally destroyed one can set up a tent with a telephone line outside the front door and with a list of patients due one can reconstruct records and re-schedule appointments until the premises are fully functional again. Without this book a dentist might as well go home. Consequently a dentist has to consider very carefully whether to commit this vital aspect of his/her practice to an electronic form which may be subject to the vagaries of an irregular power supply, corruption of storage media and the sundry other faults which can occur. To back up one’s records every time a fresh appointment is made or one deleted from the ‘book’ would be counterproductive in terms of time even though it is essential if the possibility of either missing a vacant time slot or double-booking is to be avoided. An actual appointment book can be kept in a fire-proof safe for peace of mind.

In addition to this, the software available at present for this function will only display, at best, one day per VDU screen (some only half a day) per dentist. A good receptionist can keep a visual image in mind of the black spaces in an actual book and can turn a page to ‘bring up’ a whole week at a time much quicker than any software can on a screen.

To go back to the function of computerisation of clinical records, one has to realise that for this to be fully effective there has to be a terminal and screen in each surgery with central mass storage as well as a terminal, etc, at the front desk. This again raises the question of cost: even using micros for only two surgeries and reception on this basis with, say, 10Mb storage will put the cost towards the five-figure mark, which becomes very expensive in the context of a small dental practice. The actual storage figures for dental records with chartings for each patient may be in the range of 500-700 bytes per patient per course of treatment and this multiplied by approximately 3000 patients per dentist gives some idea of the basic storage needed to keep clinical records. Details of treatment have to be kept for at least two years after completing a course of treatment and this, allied with all the other office functions needed, suggests that the 10Mb mentioned above could be a conservative estimate for a practice containing three or more dentists.

The other main problem concerning dentists at the present time is the possible computerisation of the NHS claim form FP17. This is a complex form which has to be filled in accurately so the dentist can be paid by the NHS. It contains details of the patient; name, address, clinical charting grid, a minimum of seven different dates to be filled in and various other details. Software has been written to cope with this so it can be printed out after the data has been put in from the handwritten clinical notes. The problem with this is that the slightest change in the format of the grids, etc, on the FP17 would mean rewriting this software. A suggestion has been made that the central collating body for these forms could use ‘light pens’ to read any printed codes produced by any printer, enabling a dentist to use whatever internal record system is desired. This problem still has to be resolved and will depend on whatever change in method of remuneration of dentists may be applied in the future.

The only other main office function for which a computer is often used and not yet mentioned in connection with a dental practice is the use of word processing. This is not generally a great necessity in a dental practice. Recalling patients every six months is often a feature of a dental software package and would incorporate a print-out (hard copy) format.

In summation, one can state that the small system with a couple of disk drives, screen and printer (not necessarily of letter quality) with a good database software package at about £3000 is a viable proposition for even the single-handed practitioner. The limitation of use to office procedures only is still worthwhile, even solely on the basis of eliminating lots of pieces of paper. Clinical records require considerable mass storage, sophisticated software and even provision in the actual surgeries to accommodate the extra terminals needed.

First published in Personal Computer World, April 1983

A Piece of the Action – The Multi-User Sig/Net

Terry Lang investigates the benefits – and drawbacks – of a shared access system from Shelton Instruments.

Shelton001

Front view of a multi-user system with hub and satellites stacked together.

In building their phenomenal success, microcomputers have had the advantage of needing only to provide an operating system which supports just a single user. This has enabled them to avoid much of the dead weight which encumbers mainframe systems. However, there has always been a need for micro systems to support a small number of simultaneous users – for example in neighbouring offices in a small business. (Such users will always need to share access to common data for business purposes. Sometimes users choose to share peripherals – eg, hard disks or printers – simply to save money, but the economic reasons for this latter type of sharing are likely to weaken as the technology continues to develop.)

Even in a shared microcomputer system, it has generally been economic to provide a separate processor for each user, and thus the spirit of simplicity in the operating system can be maintained. Nonetheless, the administration of the shared data does impose an additional challenge, and it is always interesting to see how this challenge is met.

In this article I will be looking at the way this is tackled by the Sig/net system produced by Shelton Instruments Ltd in North London. During a previous incarnation I was responsible for buying a large number of single-user Sig/net systems, which met all my expectations at that time, and I was keen to see how the multi-user combination would be carried through.

Hardware

Shelton002

Rear view of multi-user system showing ribbon bus cable and terminal and printer ports.

The original single-user Sig/net is itself based on a ribbon-cable bus which connects together the internal components of Z80 processor and memory board, disk controller board, and communications boards (serial and/or parallel). In developing a multi-user system it was therefore a natural step to extend the bus cable to simply chain on other systems, each supporting a single user by means of a processor and memory board. This is illustrated in Figure 1.

Figure_001

Fig. 1. Modules making up the ‘hub’ and user satellite processors on a multi-user system.

The central or ‘hub’ system with one floppy disk and one hard disk fits in a case of its own. The satellite user systems fit three to a case, and these cases are designed to stack neatly with the ‘hub’ as shown. As many satellite cases as may be needed can be chained on via the bus cable. (I understand a 14-user system is the largest installed so far.)

The basic component boards, with the exception of the new ring-ring bus connector, are all those which have proved very reliable in the original single-user system (Since the company has a considerable background in process control reliability should be something it appreciates.) To my mind the cases do run rather hot but I am told this has not caused problems.

The bus cable runs at a maximum speed somewhat below 1 MHz, not particularly fast but adequate for the purpose, as I shall discuss below. More significantly, it has a maximum length of only a few feet. This is sufficient for stacking the cases as illustrated in the photographs, but does mean that all the processors and disks have to be sited in the same room. Of course the user terminals are connected via standard RS232 serial communications ports, and can thus be located wherever required (using line drivers or modems for the longer distances).

Alternatively, it is also possible to connect a complete satellite to the hub via an RS232 link. This would enable a satellite with its own floppy disk to be placed alongside a user and distant from the hub hardware, but it would mean that access to the files on the hub would be correspondingly slower.

Both the hub and the user satellites use Z80 A processors running at 4 MHz. For the purposes of the standard PCW Benchmark programs, which are entirely processor-bound and make no reference at all to disks, it didn’t matter at all that a multi-user system was involved, since each Benchmark program ran in its own satellite processor plus RAM board, unaffected by the rest of the system. The Benchmark times, with the programs written in Microsoft Interpretive Basic, are given in Figure 2.

These times are as good as one would expect from an equivalent single-user system and illustrate the benefits (or perhaps one should say the lack of drawbacks) of this kind of multi-user sharing. (Of course, where user satellites share access to the common hub filestore, then the user programs will slow each other down – this is discussed in detail below.)

The one-off end-user prices for multi-user and single-user Signet systems are given below. These represent very reasonable value for money. Much of the system is of British manufacture or assembly, which should help price stability. It should be emphasised that in addition to the prices quoted you would require an additional terminal for each user. (Integral screens and keyboards are of course not appropriate to this configuration of centralised hardware. This does permit a range of terminal choice according to need)

An important feature is the ease with which a single-user system can be upgraded to multiuser. The old single-user system simply becomes the hub, with one of the floppy disk drives exchanged for a hard disk. Multi-user satellites are then added as required. If you find a dealer who will give you a reasonable trade-in on the exchanged floppy, then the upgraded system should cost you the same as if you went multi-user straight from the start – a cost-effective upgrade path. Since a satellite case and power supply can be shared between three users, it is most cost-effective to add three users at a time, for a cost of £622 per user (plus terminals, of course).

For those who need such things, other peripheral hardware is also available – eg, graphics drivers, A/D converters, industrial I/O, S100 bus adaptor.

Shelton003

Inside view of case with three user satellite processors and common power supply.

Sharing a hard disk

So much for a single user accessing one file over the McNOS network. As the next step, I looked at the facilities for several users to access different files on one hard disk. McNOS provides for separate users to be identified by distinct system ‘user names’, and each user name is protected by its own password. All files remain private to their owner unless explicitly made public via the appropriate command.

Each user name is provided with both a main directory and with up to 16 subdirectories (just as if the user had 16 separate floppy disk drives) identified by the letters A to P. Thus instead of the traditional CP/M prompt of the form

A>

where A identifies the logged disk drive, in McNOS this becomes

A.C>

where A identifies the hard disk drive and C the default sub-directory for this user. Whenever the user creates a new file, space for this is taken from wherever it can be found on the drive. Some multi-user systems divide the hard disk up in advance, so that each user has a fixed allocation but whilst this protects other users against an ill-mannered user grabbing more than his share of space, it also means that space allocation has to be fixed in advance. In a well-ordered community, the McNOS approach is much more flexible.

To measure the effect of sharing the one disk. I repeated my Benchmark, with a different file on the hard disk for each of two users. When I ran the program for just one user alone, the execution time was 33 seconds: when I did the same for the second user alone, the time was 54 seconds. This very large difference was due to the different positions of the two files on the disk, thus requiring different amounts of head movement (This is one of the bugbears for would-be designers of benchmarks for disk systems!)

Then to measure the effects of sharing, I set the second user program to loop continuously and timed the program for the first user. With this sharing, the execution time increased from 33 seconds to 205 seconds. This increase is explained partly by the competition for buffer space in the hub, but I suspect largely by the greatly increased disk head movement as the head moved constantly between the two files. This is inevitable for physical reasons under any operating system. Sharing access to one disk is going to have a big impact if a number of file-intensive activities are run at the same time; but this should not be a problem for programs where disk access is only occasional (eg for occasional interactive enquiries).

Sharing a file

However, as I indicated at the beginning of this article, the real reason for a multi-user system is often to provide different users with shared access not just to the same disk, but to the same file at the same time (eg, for stock enquiry and sales order entry from several terminals). But if one program is going to read a record, alter the contents, and finally rewrite that record, then that whole updating process must be indivisible. (For if a second program read the same record at the same time and tried to rewrite its new data at the same time, the two processes would interfere with each other). To overcome this problem of synchronisation, a ‘locking’ mechanism (sometimes called a ‘semaphore’) is required, whereby a process carrying out an update can ‘lock’ the record until the update is complete, and whereby any other process accessing that same record at the same time is automatically held up until the lock is released.

On a mainframe database system it is generally possible to apply a lock to any record in this way. However, this can be rather complex (for example if two adjacent records share the same physical disk sector, then it is also important not to allow two programs to buffer two copies of that same sector at the same time).

In keeping with the spirit of micro systems, McNOS implements a simpler compromise mechanism, by providing one central pool of ‘locks’ stored as 128 bytes in the hub. A user program can set a lock simply by writing to the appropriate byte, and release it again by clearing that byte. It is up to programs which wish to share access to the same data to agree on which locks they are to use and when they are to use them In general the programs will by agreement associate a lock byte with a whole file rather than with an individual record as this avoids the problem of two adjacent records sharing the same buffer. It also avoids the problem of the restricted number of locks (even if a bit rather than a byte is treated as a lock, this still only provides 1024 locks).

McNOS maintains the lock record on the hub as if it were a file (of just one record) called LOCKSTAT. SYS, though this ‘file’ is in fact stored in RAM and never written to disk. A user program which wishes to set a lock simply generates a request to read this record. If the record is returned with byte zero set to non-zero, this indicates that some other process is itself busy setting a lock: the program must then wait and try again later. When the record is returned with byte 0 set to zero, this program may examine the bytes (or bits) it wishes to set and if it is clear to proceed set them and rewrite the record (The reverse process must be followed later to clear the bytes and hence release the locks.)

To measure the impact of this locking mechanism, I next changed the Benchmark program for the first user so that it shared exactly the same data file as the second user. McNOS provides a particularly convenient way of doing this, for it is possible to create in one directory entry a pointer not simply to a file, but rather to another file entry in another directory. Thus all I needed to do was to change the directory entry for the first user so that the original file name now pointed to the data file of the second user. Running the Benchmark for either user alone now took 54 seconds (ie, I was using the ‘slower’ of the two data files as far as disk head movements were concerned). I then changed the Benchmark program itself for the two users, so that each read/write pair was bracketed by a lock and an unlock operation as would be required for sharing the file. Now running the Benchmark for either user alone took 106 seconds – a measure of the overheads of using the locking mechanism.

Finally I ran the programs for the two users simultaneously. This meant that the overheads of the locking mechanism, of buffer sharing in the hub and of competing head movements were now all included resulting in a total execution time of 262 seconds. All of which simply shows that the sharing of data in this way consumes resources (as usual you do not get ‘owt for nowt).

Another important resource is of course software. Just because the operating system provides a locking mechanism does not mean that you can take any CP/M system, run it from two terminals, and neatly share simultaneous data access. This will happen only if the program is explicitly written in the first place to use the locking mechanism. At least two general data management packages are already available which use the McNOS locking mechanism: ‘Superfile’ from SouthData of London (reviewed in PCW January 1983), and ‘aDMS’ from Advanced Systems of Stockport (PCW review shortly).

Multi-user software

Thus in the Signet multi-user configuration we can see hardware which is a simple extension of a single-user system. However, the software extension is not quite so straightforward when moving from a single-user to a multi-user operating system. The need for such a system of course became apparent some considerable time ago. Unfortunately, the first attempts by Digital Research to extend CP/M in this direction ran into a number of difficulties. Therefore Shelton was obliged to look elsewhere, and eventually obtained the McNOS (Micro Network Operating System) system from its originators in the USA. McNOS aims to provide a file store and printer spooling system in the hub processor, plus a CP/M-like environment for each satellite user, and the necessary communications software to link them together. As others have found who have followed the same route, a lot depends on exactly what you mean by ‘CP/M-like’. While a well-behaved program may just use CP/M by calling on it in the approved fashion for any functions it needs to be carried out many other programs also call upon the internal subroutines of CP/M or utilise direct access to its internal data tables.

Indeed, in the early days of CP/M, many programs were forced to employ such dodges in order to work at all. (One well-known package reportedly follows each call to write to a file by a ‘close’ call in order to force the writing of any partially filled buffers; though the file is thus repeatedly closed and never subsequently re-opened, earlier versions of CP/M would still allow the following ‘writes’ to take place.) For such programs any strict implementation of CP/M is sure to stop them running. With additional work by Shelton, these problems were eventually overcome by relaxing the conditions of the CP/M-like environment to permit such dodges to be employed.

In the single-user versions of CP/M such dodges did little harm since, if the worst came to the worst, the user would only upset his own program. In a multi-user situation, however, it must be realised that such dodges, if incorrectly employed by a user program, can upset other users as well. This has to be accepted as the price of making sure that the whole wealth of existing CP/M software will continue to run in the multi-user environment.

Before looking at how disks and files can be shared between several users, I thought I should first check how much delay is introduced into file accesses for a single user with a file which is no longer on his own satellite system, but which is now accessed on the hub through McNOS over the connecting lines. For this purpose I constructed a file of fixed length records, and wrote a simple Basic program which read and then rewrote each record. Records were taken alternately from either end of the file, stepping up from the bottom of the file and down from the top until the two met in the middle, thus ensuring a reasonable spread of disk head movement. To provide a norm for my measurements, I first ran this program in a true single-user standalone CP/M Signet system with floppy disks, and obtained an execution time of 257 seconds. Next I transferred the floppy disk to the hub of the multi- user system and re-ran the program from a satellite. The first thing I noted (cynic that I am) was that the program still ran, and that the floppy format was indeed the same under McNOS as CP/M. Would you now care to guess the execution time running over the network? In fact it was 53 seconds, a reduction of almost 80%! The reason for this of course (and it may be ‘of course’ now, but I confess I didn’t expect it at the time) is that much of the 64K RAM in the hub system can be devoted to file store buffering, thus minimising the number of physical transfers actually needed. (If other users had been running at the same time, they would have taken their own share of these buffers. Where there is competition, McNOS sensibly arranges to keep in its buffers that information which has been most recently accessed.)

Shelton004

Processor/memory card, serial communications card and bus interface to support a single user.

The terminal command language

In the beginning were mainframes, which ran programs in batch mode. Because the user could not direct his program from a terminal but had to think ahead for every likely eventuality, the operating system provided a ‘Job Control Language’ to help in directing the compiling, loading and executing of programs. Some Job Control Languages were so elaborate that they could even be used to solve differential equations (or so rumour had it). Then came the micros and operating systems like CP/M, with very simple commands which could be used from terminals. This command structure could hardly be dignified with the title ‘language’ (even though SUBMIT and XSUB do give the possibility of issuing several commands at once). There does seem a need for a more comprehensive job control language, even on micros, for tailoring packages and giving the user turnkey systems. (Sometimes this is done through a specially written program, or via a general purpose ‘front-end’ package which sits on top of CP/M)

McNOS tackles this situation by providing its own job control language, complete with variables, arithmetic and assignment statements, conditional expressions, and subroutines. All this is of very great power, but at the cost of considerable overheads in processing time. To test this out in a pale imitation of those who solved differential equations with the job control language on mainframes, I coded one of the PCW Benchmarks in the McNOS command language. This ‘program’ is shown in Figure 2. I estimate (since I didn’t feel inclined to wait for the whole 1000 iterations to finish) that this program would have taken over 14,000 seconds to complete (compared with 9.6 seconds in Basic)! Time may not be so critical in more typical job control situations, but it must be possible to do better than this. However you do not need to use it if you don’t need it. It is perfectly possible to stick to a very small subset of the simple commands, which then makes the system very like CP/M. Unfortunately, of course, it can not be exactly like CP/M because it is necessary to maintain a unified underlying syntax capable of supporting the larger language too. As a fairly experienced user of CP/M I must say I had no difficulties with the differences, though they would prevent a novice user from working with a standard CP/M primer as a guide. (I have heard it said that at least one user was so impressed by the McNOS command language that he asked to have it implemented on his single-user CP/M systems as well).

Figure_002

Fig.2. Coding of PCW Benchmark Program 3 in McNOS Terminal Command Language.

Future developments

A user who is just starting on a microcomputer development which requires only one system now but which could expand to become multi-user later, could well choose a Sig/net system for its development potential. If Shelton maintains its record in exploiting its technical expertise, then it would be expected that other developments would be on the way. I understand that one of these developments is the provision of a local area network facility based upon the Datapoint ARCNET approach. This will be used instead of the current ribbon bus to provide high speed communication over much longer distances, and thus permit the siting of user satellite systems away from the central hub. I must point out however that this is not yet an available product or, as Guy Kewney so aptly put it in this same magazine ‘the future is not now…’

Conclusions

The Shelton Sig/net system is based on good hardware and provides good value for money. The system provides a convenient cost effective growth-path for the user who wants to start small but expects to expand to a multi-user system later. The McNOS multi-user operating system provides convenient facilities for users who wish to share data between a number of terminals and a number of CP/M programs, provided this can be done on a scheduled basis (ie, no file being used in update mode by more than one user at a time). It is also possible to share simultaneous update access to the same data files with programs written specifically to take advantage of the McNOS ‘locking’ mechanism. The powerful McNOS terminal command language would be useful in some circumstances, but can be slow to use.

Benchmarks  
BM1 1.1
BM2 3.4
BM3 9.6
BM4 9.3
BM5 10.0
BM6 18.1
BM7 28.9
BM8* 51.3
Average 16.5
*Full 1,000 cycles  
For a full explanation of Benchmark timings, see PCW November 1982

 

Prices – Multi-User  
Hub filestore, 1 x 400K floppy  
Hard disk, 5.25Mb (formatted) £2,695
Hard disk, 10.5Mb (formatted) £2,954
Hard disk, 15.75Mb (formatted) £3,195
Hard disk, 21Mb (formatted) £3,500
Satellite case  
1-user (Z80A, 64K RAM, 1 x RS232) £1,100
2-user £1,550
3-user £1,865
Single User  
Z80A, 64K RAM, 2 x RS232  
Floppies 2 x 200K £1,390
Floppies 2 x 400K £1,690
Floppies 2 x 800K £1,890

First published in Personal Computer World magazine, April 1983

Microtan 65 Review

Microtan_65_001

Just another 6502 system? We think not. Microtan’s expandability is almost second to none and it could be a winner.

By Henry Budgett

The ideal system in most people’s minds is one that is as cheap as possible, provides the most facilities, is expandable to the limits of its design and can be obtained piece by piece as the money is saved. Up to now there have been several systems that have sought to achieve these varied aims, and the results have been many and varied.

The machine reviewed here is another contender in this field and certainly seems to be set for success where others have not. Based on the 6502 CPU, the same chip as used in PET and Apple among others, it has several very interesting items to offer.

Concept of A System

The usefulness of a computer on a board is limited, the usefulness of a system with attendant peripherals is much greater. The ideal balance is struck when the single board can become part of a system and thus have the capability of fulfilling the needs of both markets.

Microtan has been designed in this way, the complete system has been planned and is then offered board by board. This review is only going to cover the basic board but mention will be made of the available expansion to construct the system. Table 1 gives details of the various stages that are available, in their various configured forms.

Assembly Or Assembled?

I built the Microtan from a kit, something that I believe is worth doing as you not only save money but you do get an insight into how the hardware is strung together.

Presentation is superb and to anyone who is competent with a soldering iron this should represent no more than an evening’s work. Please note that the PCB is double sided and through-hole-plated so you must use a fine tip on the iron and fine solder otherwise you will have problems.

The manual that is supplied covers all the areas needed to construct the kit and get it up and running. It covers other areas that I will mention later. The only serious omission is the lack of a circuit diagram, but this is being rectified I gather. You will need a power supply, the 5 volt supply that we published in CT serves admirably or you can buy one from Tangerine.

The true test of any kit is whether it works, it did in its basic format and with the graphics option in place but it died when I tried to add the lower case option. Immediate thoughts of dead ROMs were not correct, the eventual culprit was a tri-state device that was permanently tri-stated. Quick work by Tangerine meant that I was back on the screen before the postman had called twice.

Micro Monitor

The old question of “How much can you fit into a pint pot?” rears its ugly head with Tanbug, the 1K monitor supplied as standard. The answer in this case is “Enough!”. At this stage you have a system that can only deal with machine code and a glance at Table 2 will show that there is only one possible omission from the monitor, that of cassette handling. Well, you don’t have a cassette interface yet so what are you worrying about? If you are going to expand to Tanex, which has that necessary interface, you get the routine for handling named files which you can either load up yourself or get in an EPROM that plugs in to a socket and is called through Tanbug. The cassette handling is at a choice of 300 or 4800 Baud so you can’t even boil the kettle let alone drink a cup of coffee while loading programs.

What does Tanbug have that sets it apart from other monitors? Two things really, you get a full listing of the firmware with notes and explanations and you don’t get any bugs, at least I haven’t found any yet. It does all that the Microtan user will require and if you ever get big enough to warrant it there is a bigger version called XBUG lurking in a dark corner.

Manual Means Handy?

The little orange covered book that is supplied is worthy of a mention in its own right. OK, it’s not perfect but it is detailed and concise. One or two errors have escaped correction but nothing that will cause the crashing of programs or other damage. The book fits into a ring binder and will be joined by the manuals for Tanex and the other family members, a neat concept in its own way.

For a change the manual is logical, it explains the concept of the board, then the system, then the details of the 6502 with the complete instruction set and then a very detailed chapter on the monitor and its uses – complete with the listing and finally it gives you a couple of games. It is essential to read the whole thing through from cover to cover before starting to play, the unit is complex and should be understood before anything is attempted.

What You Get

Once the board is built and the manual read you are ready to go. All you need now is a black and white TV and a 5 volt power supply at about 1 amp. Connect up, turn on and hit reset. The screen is covered in a pretty pattern with the words TANBUG at the bottom followed by a prompt character. At this point we find the only serious problem with the system. You have a ? on the screen but you are told that you should have a square blob, have you blown it up? No, you haven’t got the lower case option. It is explained in the manual but it is very unclear and has caused much confusion and alarm both in the office and outside.

So, you have a working system. Machine code programmers can now go and have a ball, the rest of us start learning. If you are a dedicated BASIC person Tanex is a must, throw away the Hex keypad (superb thought it is), plug in the full ASCII, the system works out which you are using, and let yourself go with a 10K Microsoft BASIC.

Points worth of note, and praise, are the rock steady display on your TV, the VDU RAM is only accessed when the system RAM is not so you don’t get the usual flicker, the excellent Hex keypad and the almost unbelievable packing density. Because the system is based around the 6502 comparisons with the Acorn, reviewed in August 79, are almost inevitable. With Microtan you get a proper VDU as opposed to an LED display, a decent keypad that is separate and a slightly more powerful monitor but you do lose the cassette (at this stage).

The Guts Of The Matter

Figure_001

Fig.1. Microtan’s architecture, all on one board to!

Because of a lack of space on the board certain apparently ignored features are implemented at other points in the system. Figure 1 shows the architecture of the board, the keyboard interface is intelligent in that it detects what type is being used. The memory map of the system, see Fig.2, appears to be rather limited, full decoding is done on the Tanex board and gives the map shown in Figure 3. This is not the disadvantage that it might appear to be, it allows the contents of RAM on Microtan to be protected against DMA as are the I/O ports and the ROM area. Whilst on the subject of I/O it is worth noting that you get a 1K area that is addressable as I/O, this compares with a maximum of 256 on devices using the Z80 or 8080.

Figure_002

Fig.2. The simple memory map produced by Microtan

Figure_003

Fig.3. Once you’ve added Tanex you get a proper memory map, which is fairly impressive.

The system expansion is shown in Figure 4, full details of the bus structure are given along with notes for DIY people. The address bus buffer chips are supplied as part of the Tanex unit, so don’t worry about the empty sockets.

Figure_004

Fig.4. How you expand through Tanbus

On Board Options

Despite the fact that the basic Microtan packs in a 6502, keyboard interface, VDU, 1K of RAM and 1K of monitor ROM there is more to come! As seen from the previously mentioned Fig.4 the address bus buffers fit on, but that’s not the end. You can have lower case alphabetics, not essential at this stage, and pixel type graphics, sometimes called “high resolution” but really made up of little squares not dots. Tangerine are quite honest about them and call them “Chunky” which is a very apt description, they are good enough for Teletext simulations and games etc.

Because of the ingenious VDU design it is quite possible to run a program that actually resides in the screen memory without bombing everything, try that on your system.

Expanding Horizons

Glancing back to Table 1 you can see the basis of your system emerging. The rest is coming shortly and completes the story. Tanram will be the next board to go on sale and offers 40K of memory on a single board and this will have the capability of bank selection so RAM freaks can have the odd megabyte or six if they want. You may have realised that the system is now full, see Fig.3. Next on the stocks is Tandisc, offering you the floppies that you dream of, up to four double density units are planned.

Microtan_65_004

The Microtan board installed in the mini-rack

Microtan_65_003

Tanex fits on top in the mini-rack system, along with the power supply and Hex keyboard.

Housing all this exotic hardware need not be a problem either, the case that Tangerine supply will hold Microtan and Tanex complete with power supply. The other style that you could use is a card frame, I am building my system in a Vero unit, assembled from System KM4C parts which also offer such goodies as front panels and modules. However you could design your system to fit into a VDU case and have a self-contained system, it’s up to you.

Microtan_65_002

The author’s system growing inside a Vero rack.

Summing Up

Microtan, and its attendant extras, offer the first time buyer a low cost entry point into computing. Taking a boxed two-board system with all the options, power supply and key board you have a more powerful unit than a PET, it has more I/O capability and at £350 it is a lot cheaper!

The product appears to have been launched with a great deal of thought and planning, in itself a change from some rivals, and seems to have found a niche in the market almost overnight. The only thing it hasn’t got is a “second generation” CPU such as a Z80 or 6809 but that doesn’t seem to be too much of a handicap, the dedicated machine code programmers among you might disagree but no-one else has!

Table 1. The various system configurations for Microtan
Board Microtan 65
Features 6502, 1K RAM, 1K ROM, 6 I/O ports
Options Pixel graphics, lower case alphas, address bus buffers
Need to run TV, Hex keypad, 5V PSU @ 1A

 

Board Tanex
Features 1K RAM, 16 parallel I/O, TTL serial I/O, cassette I/O, 2 by 16 bit counter timers, full memory map, data bus buffers
Options 6K RAM, 4K ROM, 10K Microsoft BASIC, double above I/O plus RS232/20 mA serial with full modem control

 

Board Tanram
Features 40K mixed static and dynamic RAM

 

Board Tandisc
Features Control of four drives
Extras Motherboard, case, power supply, Hex keypad, ASCII keyboard

 

Table. 2 The available monitor commands on Tanbug
Monitor Command Function
M(add)(term) Modify memory locations, terminator type allows step through, cancel or jump out.
L(add),(numb)(term) Lists the contents of specified memory locations in tabular form.
G(add)(term) Sets internal registers and executes program at address given. NB cursor disappears.
R Sets memory modify command to register mode. Allows the 6502s internal registers to be altered.
S Sets single step mode, see P & N
N Resets to normal mode from single step
P Causes monitor to execute next instruction, can be set to execute n instructions. Gives display of all registers and returns to monitor.
B(add),(numb)(term) Sets breakpoint at specified address, up to eight are allowed. All registers are displayed and P command may be sued to continue.
O(branch add)(dest add)(term) Calculates offsets between specified addresses for use in branch arguments.
C(start add)(end add)(start add dest)(term) NB (term) can be CR, LF or SP Copies memory locations and blocks.

 First published in Computing Today magazine, June 1980

Zenith Z89 Reviewed

Zenith Z89_001

Heathkit’s entry into the world of small systems could represent a breakthrough in affordable computing.

By Ron Harris

The Zenith Z89 is a dual processor system based upon the Z80 CPU chip. In effect it is two machines in one box. The VDU has its own controller, totally independent of the main CPU. Standard memory configuration is 48K of user RAM with 8K of system RAM and ROM. The keyboard is a fairly standard QWERTY affair, with a 12 key numeric pad also adorning the front panel. The VDU has… look – hold it here a minute. This machine has more facilities than I’ve had hot dinners and if I go on listing and describing we’re all gonna be here until the sun goes cold and England win the World Cup again.

Table One is a summary of the hardware features of the system and after you’ve glanced down it I’ll go over some of the more interesting abilities possessed by the unit.

Any Port In A…?

Zenith Z89_005

Expansion possibilities revealed

There now. That didn’t take long. One thing not mentioned are the output ports to allow for the hanging on of peripherals. These are RS232 standard with a data rate of between 110 and 9600 bps, user specified. Parity can be odd, even, or anything else you can dream up, it is flexible.

The system as a whole is exactly that – flexible. The machine makes use of its size to offer the user a flexibility and potential undreamed of – and undreamable – in the lower priced computer systems.

At this price, which could be described, at present, as lying above the high priced home machines, the Sorcerors and the rest and yet below the lowest end of committed business systems, who can be expected to seek out and purloin a Z89? Well, anyone needing a very versatile and powerful computing tool, with an excellent built-in disc facility and great ‘keyboard’ power would be advised to look here. The Z89 can be an absolute top-class home system, or a very useful business machine for the smaller company, take your pick.

Figure_001

Fig. 1. And this is just a system diagram!

It seems to fulfil what many of the earlier machines promised – but fell short of. It is truly a complete, yet expandable, computing system. It arrives with built-in disc drive and facility for adding on an external Z87 dual disc. Each ‘diskette’ has 100K of storage and is of ‘hard sector’ type, which means that the size of each sector is hardware determined by the PCB, not by the software controller. This in-turn means that the sector size is fixed. Sectors are allocated to files in ‘increments’ of two ‘256-bytes’ as required by the operating system.

What Comes With…

Heathkit supplied us with all the manuals you ever dreamed of, including the one for the WH 89 – the kit version of the Z89. Mind you, kit is a misnomer really, as most of the PCBs arrive assembled! Module assembly would be a better term. As usual for Heathkit, the documentation is faultless, if a little daunting in this case. We got a huge binder for CPM, one for HDOS, another two for BASIC and a three inch thick WH 89 manual with circuit diagrams. The latter are complete down to component level, with full overlay documentation.

Well, I’ll believe they’ve thought of everything – lest ten more manuals drop through my desk. You know, with all this paperwork – most of which contains a “What to do first” section, couldn’t they add just one more little bit? A small, totally separate, approachable little pamphlet for each configuration, telling you how to get it up and DOING something, as opposed to sitting there humming gently and looking smart. On behalf of all the people who will buy this machine, take it home, put the plug on, switch on get “H:” on the screen – and get that empty “Oh God what now?” feeling in the pit of the stomach, PLEASE Heathkit?

Still, back-up looks like being very good and I doubt if even the most obnoxious purchaser would find himself turfed out in the street, box in one hand and manuals in the other.

Heathkit were very helpful indeed to us – even putting HDOS onto each of the discs they loaned us to save messing about having to keep shuffling the source discs.

Zenith Z89_002

The hard sectored disc can be back up by two external brothers.

Zenith Z89_003

All neatly packed in with acres of room to service.

Soft Touch

After experimenting with both the CPM and HDOS we were provided with, I developed a preference for HDOS to the extent that CPM stayed in its folder after the first couple of runs, unbidden while HDOS spun its triumphant way across the heads.

Somehow HDOS is simply more usable and flexible – it lets you get at the material it is handling with the minimum of interference and the maximum facility. The perfect librarian, in fact – and what else can you ask from a disc operating system?

The folder for HDOS is very well written and produced and the opening chapters nicely sectioned with “First time through” lists every now and then to help a new convert learn his art. That little pamphlet I wanted could be no more than these sections extracted and re-presented. As it is, if you don’t know where to look you’ll never find it!

My advice to any new or aspiring owner of a Z89 is to sit down, with a cup of tea and the HDOS manual and READ IT. It is approachable and conversational in style and easy to digest, managing to avoid the usual half incomprehensible flood of abbreviations and jargon that swamps some rival efforts. A new user needs to be told what he has obtained for his money, not shown what a clever little boy the manual author can be. Heathkit could hold classes for the opposition on producing manuals – if any of them would bother to go, that is.

Figure_002

Fig. 2. Schematic of the elephant’s brain!

Side One, Track One

Supplied with the Z89 is a ‘distribution diskette’ as they call it, containing the operating system, HDOS, with a few very useful little ditties, like BASIC, DBUG, EDIT and ASM. I’m afraid that in the space I have in this magazine I can do little but whet your appetite as to the scope of these files. Suffice it to say:

  • BASIC an extended 16K BASIC with all that implies. This is the ‘Benton Harbour BASIC’. Microsoft BASIC 80 is also available, but requires 28K of RAM, and thus will run best on the minimum of a 32K system. No problem with a Z89. This includes line renumbering, amongst other things, and sufficient facilities to make any BASIC nut offer up an arm or two.
  • DBUG makes use of HDOS to allow for full debugging of machine-code programs. Will display and alter the contents of any specified memory location, or 8080 compatible register; will execute a program either completely, or line by line; will load or dump programs onto discs, printers VDUs etc; and will insert ‘breakpoints’ executing several instructions then halting with control returned to DBUG.
  • EDIT the Heath Text Editor. Will do nicely as a word processor, providing good editing facilities with 15 editing commands. You could write the annual report on this – or a note home to granny asking how the budgie is doing. Works very well too for editing BASIC programs.
  • ASM Heath Assembly Language Program. Once you’ve got used to the EDIT you can use ASM to run source programs on the Z89. For best use you will have to know the 8080 pretty well.

As I said before there is much much more to these titles than I could get into a single issue. All I can do is recommend the supplied software very highly. It is well thought out and nicely tailored to the system. Useful and useable.

Hard Times

Zenith Z89_004

One of the two main circuit boards with its daughters

With the hardware configured as two interactive portions we have a potentially very powerful beast and a potentially confusing one. The key to the whole operation is a little key tucked at the top left of the keyboard. Called OFF LINE, it means exactly that. Press this down and you disconnect the computer from the keyboard and screen (Fig. 3). This means of course that you can go on typing until your fingers drop off but the computer is totally ignoring you.

Figure_003

Fig. 3. A Trap for the unwary

The advantages are great. The cursor can be shifted around, lines cleared – even screens cleared – without code transmission and hence the program knowing about it. Of course if you forget to put it back on-line………………………

There are eight user definable keys strung along the top of the board, which you yourself can set up to be something worth using – instructions are of course provided to do this.

Having an intelligent keyboard takes some getting used to after more basic systems, but it is a luxury you soon learn to live with, I promise you!

First Blows

It might be illuminating to go through how you get the Z89 to run a program from scratch. Let’s choose BASIC as an example, assuming that your distribution disc supplied with the machine contains Microsoft BASIC (MBASIC).

At switch-on “H:” appears in the top left of the screen and nothing else. You place your disc into the drive – getting it the RIGHT way around and type “B”. The screen turns this into “BOOT” and a RETURN will bring you a “TYPE SPACES TO DETERMINE BAUD RATE”. You now have to hit the space bar repeatedly for a few sections so that the system can pick up the speed at which your terminal operates. Then “ACTION? < BOOT >” appears and a RETURN gets you “DATE [DD-MMMYY] ?” This is simply so the system can preface all your files with the origination date. Type it in and RETURN. A “ > ” now appears and you have loaded HDOS.

HDOS contains a test and a diagnostic routine, but we’re after BASIC, so all we have to do now is type in the file name, MBASIC and wait until the clicking and flashing from the drive ceases. The screen will display the header for Microsoft BASIC, telling you which issue it is and how much RAM you’ve got left to play with. If you’re a small systems man, being told that 21K remains free will probably induce feelings of inadequacy. Fear not. It is all under your control………(isn’t it?)

Summary

Impossible to do. Summarising a machine only slightly less complex than the Secret Of Life is too much for me to cope with. My own impression of the Z89 is that it is a well designed, flexible, well supported computer that knocks the opposition sideways. It would be equally at home on a dining-room table or an office desk and should be examined very carefully if you have this amount to spend on a system. It is worth the extra for its flexibility and power.

I wonder if Heathkit would accept a slightly used soul as down payment…………..?

Table 1. All these features add up to an awful lot of power and flexibility.
Processor Z80
Clock 2.048MHz
Memory 48K bytes RAM. 8K for systems ROM and RAM. 8K reserved.
CRT 12” diagonal, P4 phosphor
Display Format 24 lines of 80 characters, plus 25th user status line.
Display Size 6.5” high x 8.5” wide
Character Size 0.2” high x 0.1” wide (approximate)
Character Set 128 (95 ANSII, plus 33 graphics)
Character Type 5 x 7 dot matrix (Upper case); 5 x 9 dot matrix (lower case with descenders)
Keyboard 72 keys (60 alpha-numeric, 12 function control) plus a 12-key numeric pad
Cursor Blinking or reverse video block or off
Cursor Controls Up, Down, Left, Right, Home, CR, LF, Back Space and Tab, from keyboard or computer
Cursor Addressing Relative and direct
Tab Standard 8-column tab
Refresh Rate 60Hz at 60Hz, 50Hz at 50Hz line frequency
Edit Functions Insert and delete character or line
Erase Functions Erase line, from beginning of line to end of line, erase page from beginning of page to end of page
Bell Audible alarm on receipt of ASCII BEL
Video Normal and reverse character

First published in Computing Today, June 1980

Samson Reviewed

Samson-1_001

Underneath a new exterior the Samson reveals itself as an original ‘Mighty Micro’.

By John Fitzgerald

When the Editor slipped me a Samson-1 with a request to review it, I wondered what I was getting. It was a pleasant surprise to discover that the Samson is just a Sym-1 in a smart plastic case. I had played with a Sym for a few days some months before and was pleased to get my hands on one again. If you are thinking of spending your hard-earned cash on one of these space-age toys, you need to know one thing. Is it any good? I am happy to report that the Samson is good – very good.

The Samson-1

For the technically minded, a functional block diagram of the system (Fig.1) shows the major hardware features of the Samson and indicates some of the many expansion options available. The computer is housed in a two-piece plastic case. The upper section is pivoted on two plastic studs making it “click-fit” and thus easily removable. A clear plastic cover may be slid down to cover the keyboard and display. I found it easier to remove the lid completely as even with the cover slid out of the way, access to the keyboard is severely limited; requiring an awkward vertical stabbing motion.

Figure001

Fig.1 System architecture of the Samson/Sym. Enough to satisfy most single boarders.

The Samson is supplied fully assembled with two comprehensive manuals and a programmer’s reference card included. The only extras required are a 5V 1.5A power supply, suitably protected against overload, and a cassette recorder for low-cost program and data storage.

A high quality, double sided printed circuit board holds all the components including a 28 key ‘spongy-plastic’ keypad and a 6 digit 7 segment display. Also included is a piezo-electric ‘bleeper’ similar to those used in digital alarm watches. This gives an audible response each time a key is pressed making use of the keyboard a much more certain operation. Of course, it is all under software control and yes, you can play tunes on it! The ‘debug’ function is achieved with a hardware connection and this key does not give an audible response. However, the reference manual includes details for connecting a LED indicator which would easily remedy this omission. Though designated on the functional block diagram as a ‘Hex’ display, the on-board LED display consists of six standard seven-segment units resulting in the usual ‘abbreviated’ representation of the alphanumeric character set. The red display is nonetheless quite bright and easy to read. Use of a small piece of Polaroid would make it even better. A red plastic filter was included with our unit.

Sockets are provided for the MOS integrated circuits. Make sure the chips are fully inserted before applying power. A nice feature is the provision of blank sockets on the board enabling the memory to be expanded up to 4K and extra input-output to be fitted by simply plugging extra chips into the appropriate sockets. Extra RAM and a port expansion and connector kit are available as part of the Samson system. The overall layout of the printed circuit board is clean and uncluttered and component and connector positions are clearly marked on the component side in white ink.

Figure002

Fig.2 The Sym/Samson keyboard layout.

The documentation supplied with the Samson deserves a special mention. As well as a reference card containing op-codes, system addresses, etc, two manuals are supplied. One features all the information that you will ever need to know about the processor’s instruction set while the other contains essential data for the hardware orientated enthusiast as well as complete data sheets on the major LSI chips. Both are produced on good quality white paper with a wealth of diagrams and useful hints. These are the kind of books that cost you a fiver each in the shops and they come as standard issue with the Samson computer.

Chips

The heart of the system is a 6502 microprocessor running at a 1MHz clock frequency. This will be familiar to computer buffs as the 6800 derived powerhouse used in the KIM, PET, Apple, Acorn and Tangerine systems. (I wonder why hard-headed manufacturers choose such fruity names!) There are two 6522 Versatile Interface Adaptors in the basic system which handle input-output. These also contain software programmable timers which can be configured in numerous ways. In short, as their name suggests, they are versatile – very! Provision is made on board for insertion of a third 6522 if you can think of a use for it that is not already provided for. The board fairly bristles with connectors. These are high quality double sided, gold plated pads and mating sockets are provided either with the basic unit or are available as part of an expansion kit. Also present is a 6532, RAM, I/O, timer array which offers many features comparable to those offered by the 6522. What makes the 6532 special is the inclusion on-chip of 128 bytes of random access memory. This is software write-protectable and is used by the monitor to store system vectors and as scratchpad memory.

Memory

As well as the RAM contained in the 6532, 1K of RAM is provided in the basic system in the form of two 2114 (1024 x 4) chips. One 4K ROM chip holds the ‘Supermon’ monitor and there are spare sockets for an 8K BASIC interpreter and a resident assembler-editor. Pairs of 2114 chips are available as the ‘Samson Static RAM memory’ enabling expansion of the on-board RAM in 1K blocks up to 4K.

Monitor

The ‘Supermon’ monitor is the largest I have come across in a single board computer… and it does not stop there. Expansion is possible through the use of eight undefined keys (USR 0 thru’ USR7). These normally return control to the monitor via a vector address written into system RAM. By changing this address to point to a user written routine you can expand the facilities offered by the monitor in any desired way. Excellent and extensive hardware is provided on the Samson board and this is well used by the monitor which supports the following input-output and storage media:-

  • TTY – selectable current loop
  • VDU – RS232 interface. Baud rate is automatically determined by the monitor at log on.
  • Paper tape – data is stored as pairs of ASCII characters.
  • Audio cassette – two formats are available. The low speed system is KIM compatible and operates at 8 bytes/sec. A high speed mode is also provided and runs at 185 bytes/sec. A simple program is included in the reference manual enabling the generation and use of SYNC tapes facilitating adjustment of the cassette recorder. One with both volume and tone controls is recommended.
  • Oscilloscope display – this enables a single line of text containing up to 32 characters to be displayed on a conventional ’scope which is all you need to supply. A suitable software driver is included in the reference manual and instructions are given for generating your own character set.

The extensive use of command vectors enables the Samson owner to direct input-output to any chosen device(s). Some examples of how to do this are given in the manual which also contains a complete and legible listing of the monitor. This facilitates the use of monitor routines in your own programs and is an aid to anyone learning to use machine code. Table 1 shows the monitor commands and their function.

KIM Compatibility

The Samson is designed to be generally upwards compatible with MOS-Technology’s single board KIM computer. In practice this means that some of the connectors are different; for example, the Samson uses a separate connector for the power supply, and some of the signals are absent or renamed. Though both machines use the same microprocessor, the 6502, they are not directly software compatible. Inconsistencies include timer addresses and a number of monitor routines. Those most likely to concern the prospective user are the keyboard and monitor sections which feature most strongly in pre-written KIM software; for example, in the ‘First Book of KIM’. It is possible to use programs from this source. However, you will have to provide some software links to the Samson system. These are best provided in the form of subroutines which can be called when required. Here’s a tip. Remember that you must call ‘ACCESS’ before you can even begin to think of getting at the LED display.

BASIC

For anyone who turns white and shivers at the first mention of machine code, those nice people at Samson (Synertek – why pretend?) have come up with an 8K BASIC Interpreter. Supplied in the form of two 4K ROMs, it only requires plugging in to the sockets provided and a couple of wire jumper changes to be up and running.

With BASIC installed, following power-on, a TTY is logged on from the Hex keyboard or a VDU is logged on by typing ‘Q’. The monitor responds with a prompt Now if J 0 (CR) is entered, BASIC responds by asking for the memory size to be used. Any value greater than 512 bytes may be entered. BASIC will use all contiguous memory from location 0200 (Hex) to the value specified. This enables space to be reserved for machine code routines. You will then be asked to specify terminal width which determines the output line width for PRINT statements only. There is a default value of 72 characters though any value between 1 and 255 may be used. BASIC will then type out the number of free bytes, Synertek’s banner and ‘OK’. The prompt character (.) is replaced by a flashing cursor if you are using the Samson terminal.

There is no space here for a full description of the BASIC. It seems to have everything you would expect from an 8K interpreter and includes commands enabling you to use machine code routines in your programs. A sixty-page manual contains a brief history of BASIC with notes on its implementation in the Samson system and some worked examples and details of common pitfalls. There is certainly nothing wrong with the BASIC provided and it is good to see it offered as part of what looks at first glance like a simple development kit. However, I cannot help feeling that, if you want to talk BASIC, you should just go out; buy a PET, put the Programmer’s Toolkit on it and talk to that. PET speak heap good BASIC!… and the screen editing and graphics capabilities are excellent for a black and white system. The Samson is a superb piece of hardware with excellent software support and it seems foolish to ignore all that just to talk pidgin English!

Samson In Orbit

The Samson Satellite consists of yet another Synertek product, the KTM-2, in another plastic case. This is a full-size keyboard mounted on a single PCB which also contains circuitry to drive a display monitor. There are two models differing primarily in the number of displayed characters per line. The 40 character version may be used with an ordinary television while the 80 character unit requires a video monitor. An RF modulator is not supplied with either unit and must be purchased separately. Power requirements are simply 5V at about 1 amp.

Samson-1_003

A typical screen dump showing the squashed display. The Hex pair on the right is the checksum.

The keyboard consists of 54 keys which enable the full ASCII set and 128 graphics characters to be generated. Graphics and alpha-numerics may be displayed simultaneously and the cursor may be software driven using absolute or relative addressing. There are two full-duplex serial communication ports enabling the Satellite to interface to a computer and printer simultaneously. Transmission rate is adjustable between 110 and 9600 baud. There are eight ranges selected by three switches. Other switch selectable functions include:

  • even, odd or no parity
  • interlaced or non-interlaced display (an interlaced display may appear to flicker on a screen with a short persistence phosphor.)
  • line truncate or wraparound
  • choice of 50Hz or 60Hz frame rate.

Almost everything in the Satellite responds to automatic control. The cursor may be moved, screen cleared, graphics selected or deselected and reverse video turned on or off: all under software control. You enable the auxiliary communications port with an ASCII control code too!

Samson-1_004

How characters are made up on an oscilloscope display.

Samson-1_005

What you get when you jump to BASIC.

As you will see from our photos, the Satellite’s character rows are very close. This was done primarily for the graphics characters to connect in a vertical direction but does result in a rather cramped display with an awkward aspect ratio. One or two extra scan lines may be added by re-configuring some jumpers on the PCB. Full details are given in the 40 page A4 size manual which includes all the technical data required and adds some hints for users operating Synertek BASIC.

Figure003

Fig. 3. The graphics set of the Satellite terminal.

The Satellite is a well produced unit offering many sophisticated features and makes a good companion to the Samson-1. In conclusion, the Synertek BASIC and Satellite terminal are good. The Samson (Sym-1) is very good indeed and deserves to find wide acceptance in this country. If this article has whetted your appetite, all you have to do now is come up with the cash, go out and get one!

Table 1. The Supermon command set.
Command Function
M Display-modify memory
R Display-modify user registers
G Restore user registers, resume execution from PC
V Display 8 bytes of data with their checksum
D Deposit data from keyboard to memory
C Calculate using Hex arithmetic, displacements etc.
B Block move in memory
Jump (0-7) loads PC with address from system RAM
SD Stores a double byte
F Fills block of memory with chosen byte
W Write protect user RAM in 1K blocks
E Adjusts monitor to receive input from RAM
51 Save cassette tape KIM format
52 Save cassette tape high-speed
L1 Load KIM format tape
L2 Load high-speed tape
SP Save paper tape
LP Load paper tape
CR Carriage return
+ Advance 8 bytes
Retreat 8 bytes also used as delimiter
> Advance one byte or register
< Retreat one byte
USR0-7 User defined keys
SHIFT Select upper case
RST Reset
DEBUG Hardware debug function
ON-OFF  
ASCII Next two keystrokes combined to form one ASCII character.

 

Program to make the bleeper bleep, alter value at 011C to change note pitch
  100 20 88 81 JSR SAVER
  103 A9 0D   LDA 0D
  105 20 A5 89 JSR CONFIG
LOOP 108 A9 08   LDA 8
  10A 8D 02 A4 STA PBDA
  10D 20 1B 01 JSR
  110 A9 06   LDA 6
  112 8D 02 A4 STA PBDA
  115 20 1B 01 JMP LOOP
  11B A0 50   LDY 50
  11D 88     DEY
  11E DO FD   BNE FD
  120 60     RTS

First published in Computing Today, June 1980