80-Bus News


March–April 1983, Volume 2, Issue 2

Page 13 of 55

But change it must. With about 80 disks in use, the system was becoming unmanageable, and the investment in disks alone was worth a tidy sum. Three things happened to force me into making the system into what it is today. Firstly I hadn’t used the virtual disk much as the capacity with one RAM card was just too little, however, it had impressed me with its speed. MAP changed that with the introduction of their 256K RAM card. Next, the Gemini Winnie was put into use at work, and the change in operating procedure forced by its sheer size (5.4 Mbyte might not sound a lot, but you fill it and then try finding something in the directory) introduced me to using the USER areas in CP/M for the first time. I had never previously used the USER areas under CP/M as their operation under CP/M is distinctly unfriendly and result in the duplication of lots of common files thus using up more disk space. The Winnie showed me the delights of using CCPZ, a modified form of which is provided with the Winnie. Lastly two double sided quad density 80 track drives became available, offering 788K per drive, and the thought of reducing the number of disks in use really struck home.

The transformation took place one weekend shortly after Christmas, the two drives and the MAP card were fitted and apart from some aggro with one of the drives, which will cause me to have some very rude things to say if I ever meet a rep. from the Micropolis disk drive company, about their ex-factory quality control, all fired up correctly. Richard’s latest SYS, SYSB15, was reassembled to cope with the double sided drives and the MAP card; and CCPZ, which I had had for some time, but not implemented as it looked very complicated, was patched as necessary and away it all went.

The most time consuming part of the whole job was transferring my 80 odd disks from 35 to 80 track. There are three approaches one can take. The disks can be transferred from a 45 track machine to an 80 track machine using either the serial or parallel interfaces. Or you can borrow a machine which is fitted with both types of drive and PIP them across using the serial interfaces. Or, as the track pitch of the 35 track drives is 48 tracks per inch and the track pitch of the 80 track drives is 96 t.p.i, you can make one of the 80 track drives ‘double step’ reading alternate tracks and PIP the disk to the other drive (in a Gemini system you can only resort to the latter if double sided drives are fitted).

I used a combination of methods one and two. We have two machines at work, one 35 track and one 80 track, hooked together by a length of bell flex and a simple (but expensive) piece of software called BSTAM which allows the two machines to talk to each other serially at 9600 BAUD. About half my disk library was copied using BSTAM, taking the best part of a week. The remainder was copied using a machine called the Octopus at Gemini in Amersham. It’s a sort of Galaxy fitted with standard 8″ and 35 and 80 track 5.25″ drives, and has a Winnie lurking on it somewhere. It can be programmed to copy almost anything to anything and is used by software houses for just that purpose. This copy service is one Gemini normally charge for, but they wouldn’t charge li’l’ ol’ me .... would they? An afternoon spend on the Octopus finished the job. So within the week I was back to normal with a fully operating system and my library of disks reduced to just 25. I didn’t try using the third method, as I don’t like mucking about with disk primitives in case I get it wrong. Disk systems are a bit ‘Catch 22ish’, in that a non working disk system can’t be diagnosed because it doesn’t work, at least not without resorting to a ROM based operating system. Anyway it would have taken me a week to make the software work satisfactorily, so what odds, it wouldn’t have been any quicker, and I would have ended up with brain ache as well.

So the system in its present form consists of a Gemini GM813 CPU/​RAM card, a GM812 IVC card with GM821 keyboard, a GM809 FDC card, a GM822 RTC card, a MAP 256K RAM card, a Nascom I/O card and two double sided Micropolis 1015-F6 quad disk drives which give a shade under 1.6 Mbyte of disk storage. The whole lot is powered by a Tangerine 6 amp switch mode power supply made by Astec (similar to

Page 13 of 55