The discs are flying

Press, 17 June 1986, Page 28

The discs are flying

The world of the computer changes so quickly it gives me unjustified feelings of insecurity. If the world would only stand still for a second I could get a better grasp of what is happening instead of being in a semi-per-manent state of excitement, and, to a lesser extent, bewilderment at all the gee-whizz technology that keeps flooding past me. At the moment, no area is changing as quickly as disc technology — discs, disc drives and data storage. Anything you write today is out of date by the morrow.

What follows is the current situation. No doubt, by the time you read this, it will have changed. In the past few years, floppies, like Gaul, have divided into three parts. The 8-inch and 5.25-inch floppy floppies and the 3.5-inch semi-rigid floppies. (There are some other sub-species, but, for the sake of simplicity, let us ignore them). The 8-inch floppy is slowly drawing to the close of a long and useful life. The amount of information you can store on an 8-inch disc has remained relatively static compared with other sizes. These discs are still in wide use, but this is not where the excitement is, not where development is taking place. The 5.25-inch disc, its smaller sibling, is very far from dead. It is not even feeling sick. This sized disc is getting a new lease of life through new technology and through novel programming approaches which allow more and more information to be crammed on to the disc. When this size of disc was first introduced, as a miniature version of the 8-inch disc, it held 180 K of information on one side — something more than 20,000 words, but rather less than 30,000. Then, by the simple expedient of recording and playing back from both sides, which involved putting an extra read/ write head on the disc drive, this was Increased to 360 K. This now appears to be something of a standard — most PC programs originate on this sized disc — though more and more machines are being fitted with 5.25-lnch drives which will handle 1.2 megabytes (another IBM standard) on each disc. A large amount of information, as in just under 200,000 words, or a typical Robert Ludlum novel. But this, too, will change. The news is that Epson will be releasing a disc drive next month that will store an amazing four megabytes on a special 5.25-inch disc. It achieves this apparent miracle through specially made high-quality discs, compression techniques and a read/write head which is handled at a level of precision previously unheard of with floppy discs.

This is by no means the outer limits of technology. Something more than 10 megabytes on a 5.25-inch floppy is destined to be on the market in less than two years. These amazing figures come partially from a much more precise control of the read/write head, and partially from the use of a stretched surface system developed by 3M. The basic shape and size of the disc is kept standard, but the edges

and hub are slightly raised to form a lip. Across this pie dish shape is stretched a polymer film leaving a miniscule gap between the film and the disc.

Combine the flexibility of the film with this air cushion trapped beneath it and you get some very interesting effects, principally and importantly the ability to allow 345 tracks an inch — the same standard now used with hard discs — to be used for recording and playing back.

Experimental discs have already been made where this density has been Increased to 728 tracks an inch, thus doubling the density of the recording space. 3M has in limited production 5.25-inch discs which hold 12.6 megabytes on removable discs and 16 megabytes if they are left permanently in position in a hermetically sealed container. The research and development team at 3M believes 48 megabytes is attainable using this technique, and possibly much more if the principles of perpendicular recording are added. This last technique is being pushed ahead by Maxwell. It consists of making all the iron oxide particles on the disc surface stand to attention when receiving information, instead of lying around in a somnolent posture, thus allowing a greater density of useful coating and a greater number of tracks an inch.

In spite of all of this activity on the 5.25-inch front, it appears the 3.5inch semi-floppy is going to be the standard disc in the relatively near future. IBM is making this its standard, and whither IBM goes, the hearts and minds of others follow.

In its original incarnation on the Apple Lisa, this disc was single-sided and carried 360 K of data. Now it has gone doublesided and carries 720 K of »

available writing space, sometimes edging up to 800 K, and it has become the de facto standard.

sometimes edging up to 800 K, and it has become the de facto standard. But startling news is about to be announced. The Japanese manufacturers, who totally dominate the disc-drive market, will release a 3.5-inch disc drive in the next 18 months, which will hold a phenomenal 10 megabytes of information. That is 1.4 million words, per disc — believe it or not. With this sort of memory becoming available on floppies, you might imagine the curfew tolls the knell of passing hard disc. Not so. Hard disc technology still has a lot going for It. With prices dropping almost by the day, hard discs still have a lot of life left in them. Hard discs were commonly known as Winchester drives when IBM introduced them in the very early 70s. They were so expensive they were not a viable proposition unless they were part of a network where several users could access them, thus spreading the cost.

Now that some models are down below the $lOOO mark they have become fairly standard equipment on the upper range oi personal computers, and on machines like the IBM AT, they are practically

standard equipment The main advantages of hard discs are their large capacity and their incredibly fast access time. Anyone who has got used to working with a good hard disc is extremely reluctant to go back to working with the current generation of floppies. The way the hard disc gets this speed and this extra capacity is by using rigid aluminium discs — hence the name — over which the reading/writing head floats; it is never in contact with the surface of the disc. It hovers over the disc at roughly the same separation as the bits along the track, so high-density discs have the head very close indeed. Far closer than, say, a particle of dust or even a particle of cigarette ash. So close to the head and so fast is the speed of the disc that in rough proportion it is the equivalent of a 747 circling the earth, half a metre above the ground.

A hard disc takes some time — normally a few seconds — to get up to speed and so the motor is working all of the time the computer is switched on.

Because hard discs are hermetically sealed — the air in their casing is filtered down to one micron — they are extremely reliable once they have settled in. If you are going to have trouble with a hard disc it will be in the first few months.

After that, the only problem normally comes from moving the computer without first parking the head. There is a small routine held in the DOS programs supplied with a computer fitted with a hard disc. It is called something like “Parkdisc’’ or “Shiftdisc.” You need to call up these programs before you move your computer or the head may do a crash landing, right in the middle of your precious data.

Hard discs are going to be with us for some time to come, but they are going to be under a lot of pressure from ever-larger-memory floppies working from one direction and laser discs coming from another. I first learnt of the potential of laser discs in 1978 with a product called Laser Vision which held one hour of video on each side of a disc. Here was a medium almost heaven-sent for computers. The Laser Vision recorded on tracks only 1.6 micro-metres apart, giving a track density of 16,000 tracks an inch, hundreds of times more than your normal floppy and tens of times more than any normal hard disc.

Because of the way the laser worked, the quality of the disc was irrelevant to the quality of the reproduction. Even with a disc whose surface was, charitably, like a potato crisp’s, there was still no corruption, no information drop out. Shortly afterwards video tape came in to take over the saving of visual images and laser discs were then redeveloped into making noise-free musical recordings. Hence the new laser discs and disc players. If you have ever listened to one you will have realised you need to retain your ears to appreciate fully such amazing fidelity. Now, at long last, this technology has been* modified for use on computers. Information is placed on the disc by a laser which makes microscopic pits on the surface,

each pit equalling a digital signal, 0 or 1. This technology allows quite amazing amounts of information to be stored on a standard 12-cm (4.77inch) laser disc with 400 megabytes a side — 800 megabytes a disc — being apparently the current upper limit. This, too, will change. It would appear possible to include more information in a single pit by using the shape of the pit itself as an information signal.

Researchers believe they will be able to increase the number of bits from one pit from one to 10. This will mean there will be eight gigabits of information storage on a 12-cm disc — say 1200 million words or roughly 5000 Robert Ludlum novels. The mind, indeed, boggles. If you follow this theory to its end you come to the conclusion that laser memory is almost infinitely expandable. That way lies madness. Laser disc technology very early on branched off on to three different roads.

The first road is for what are now widely known as CD-ROM discs. These discs are sold with the Information already packaged on them (The “Grolier Encyclopedia” is a current and good example) and they can be used as a database when hooked up to a computer. There is an immense amount of activity in this area — much of it led by the amazing Bill Gates of Microsoft — and we should be seeing many players and many discs available in New Zealand starting at the end of this year and building into a flood next year.

The second road belongs to Worm discs — write once, read many times — where you can use the disc as a permanent storage for information. But once you have written the information to the disc you cannot overwrite or erase anything that is there. Call this the Rubaiyat mode — nor all thy piety and wit can lure it back to cancel half a line, nor all thy tears wash out one word of it.

This disc technology, which arrived in 1983 and in spite of my proud forecasts has not yet made any major inroads into the market, is extremely popular with auditors in that it leaves a permanent record of transactions as they have occurred and also a permanent audit trail. There is some resistance from the public, mainly because it has not managed to grasp how much recording space there actually is on these discs.

If you are using a laser disc which will hold 800 megabytes you can easily store 100 million words on that one disc — say 500 Robert Ludlum novels. There is no way you are going to write that much in a lifetime. No way. So the ability to erase and then save again becomes totally academic. But it would appear the public insists on it.

The third road is for laser discs which can be written to and erased many times and thus provide the public with what it apparently wants. Currently, two different methods are galloping to the post on this one and we should see them commercially available some time towards the end of next year on 5.25-inch discs.

The first method involves 3M, again, which places a metallic substrata into the disc and the laser magnetically polarises this spot so it reflects the laser in a specific way. Because the spot is polarised magnetically, it can also be depolarised magnetically and so the disc can be used again and again and again.

The second technology which has found favour with some of the Japanese manufacturers is to alter the angle of the laser beam so that. instead of actually pitting the surface it slightly changes the chemical construction on the spot where it glances. And this change is reversible. Note that this write/ erase/write system is not as easy to use as with standard magnetic discs and there is still a problem of disc fatigue if the process is carried out several thousand times. Where, you ask with bated breath, will it all end?

What follows is gues-

work, my guesswork, pure guesswork. In 10 years, personal computers will come with three different types of disc memory built in and these disc drives will be totally transparent to the user. That is, the user will not even know if they are switched on or what they are doing.

The first drive will be a 3.5-inch floppy disc, which will hold 10 megabytes. This will be linked to a 60-megabyte hard disc, which will, in turn, be linked to an 8-glgabyte optical disc, which is write/read/erase/write capable. Information will be transferred between these three discs as and

when needed without reference to the user. The floppy disc will allow the loading of programs and data where needed. The hard disc will work at high speed as virtual memory thus allowing programs larger than all outdoors to be used at speed and the laser disc will provide archival permanence. All of which is extremely exciting. Now all the designers have to do is think of a way to increase the memory on the machine by a factor of 10 so that it can keep in step, and think of enough information to put in all those wide open spaces.

It appears the 3.5-inch semi-floppy will be the standard disc in the near future. IBM is making this its standard, and whither IBM goes, others follow.

The changes in disc technology are occurring so quickly that anything you write with the most modern computer today is out of date by tomorrow. GARETH POWELL reviews the scene and gives his ideas on likely developments.