PolyDos

T.I.J. Toler

Although I have had my Nascom 2 for over 2 years, I must declare that I am still a beginner and this article is written for those who, like me, find they have much to learn.

After having played about with the usual gimicks – “Space Invaders”, “Stock Car Racing”, drawing lines on the screen etc., I decided to make the machine earn its keep or at least do something useful. My daughter, a professional photographer, wanted a system to keep tabs on her, literally, thousands of photographs, so, I decided to invest in a disc system. Having read up all the articles on discs and DOS, and all the adverts off I went ta the local Nascom dealer who sold me a Pertec single density, FD250 dis c drive and a G809 Gemini controller card.

The question then was – What operating system? – CP/M or something else? The “something else” was PolyDos which the dealer said would enable me to use my own programs as well as everything else. So, for £80 plus VAT I got my PolyDos. It consists of 2 EPROMs, a 5 1/2 inch floppy with the controlling programs and a manual.

Well, home I went with my purchases. First, to connect the drive. The G809 is an 80-bus card. When my Nascom was built we hadn’t allowed for an extension of the bus. However fortunately, the pins on the main board edge connector had not been cropped and were long enough to allow a second piece of Vero board to be fitted. So with a bit of engineering, the G809 card was fitted and the ribbon cable from the Pertec drive plugged in.

Next, the PolyDos EPROMs had to be fitted. The manual gives several options for this. I used the Nascom 2 main board block B. On LKB6, you connect pins 8 to 12, 7 to 11, 6 to 10 and 5 to 9. Then on LKS1, the manual says “connect pins 6 to 7 for XROM and 6 to 10 for D000-DFFF. This rather threw me and I probably connected both. However, I inserted the EPROMs, PD2A in socket B5 and PD2B in socket B6. Power up and “Hey Presto”, up comes “Boot which drive ?”. (No one told me what “boot” meant!!)

Now the next stage is to hit “0” – which I did. Nothing happened, no joy on the disc drive – all dead as a doornail. So, off to the dealer with my equipment. Now, unfortunately, I don’t know exactly what he did but I think he altered the connections on LKS1. They are now as follows:–

1 to 16
2 to 15
4, 7 and 10 all together
8 to 9

I suspect he also made some alterations to the RAM board as, somehow, you have to have some RAM available at C000H. However, it worked! Enter DIR;ELD, hit Enter and up comes the list of files on the master disc.