80-Bus News


January–March 1982 · Volume 1 · Issue 1

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member (current cost 5.00 per annum). Incredibly, all you pay for this software is the media cost (the disk), a nominal copying charge (1.00) and the postage. You can even send in your own blank disks, in which case you pay only 1.50. I have in fact just done this and purchased disk No. 50, which contains, among other things, a Pascal compiler! I should mention that the speed of service is not far short of “by return post” and that the UK group themselves have four disks in their own library. In case you are wondering how I can read the 8″ disks, the answer’s simple: The library is also available on 5.25″ disks, but in a single density format called “SD” format. This is the very format chosen for the Henelec system when it was originally designed, and is also the alternative format on the Gemini system. The Gemini system defaults to double density, but allows single density disks in the second drive. Thus all the library disks are easily read by these systems. In the case of the Gemini, you have the added advantage that you can copy the SD disks on to double density ones. In some cases, two of the library Volumes (each 8″ disk is called a Volume) can fit on a single 350K 5.25″ disk!

It is this compatibility that I find most exciting about my chosen system. I now have access to a great deal of software most of which is streets ahead of any that I have written. As Dave Hunt, Richard Beal and “Parky” all operate similar systems, a user of the Nascom/​Gemini stands to learn much from these people who are, for many of us, mentors in microcomputing.

To summarise the system that I eventually ended up with:

Nascom II
2 Nascom 32K RAM (A) boards
Gemini IVC board
Gemini FDC board
2 Pertec FD250 5.25″ drives

Costs for these can of course be found in the mags. In case I did not make it clear above, it is necessary to add extra transformers in the power supply to cope with the disk drives if separate drives are purchased without power supplies.

Anyone who has looked at or used CP/M will know that it was created to be essentially independant of particular hardware. In consequence, the parts of the system that handle the keyboard, disks and display etc, are all lumped together in one area called the Basic Input/​Output System (BIOS). CP/M itself is ignorant about the particular hardware in use. A program run ynder CP/M doesn’t know if the computer is a Heath, Superbrain or Horizon. It only knows that it has an 8080 or Z80 CPU. It is insulated (by the BIOS) from hardware dependant routines. The success of a CP/M implementation relies on a well written BIOS. You cannot screen edit on a Horizon, for example. When I say that there are two BIOS’s for the Nascom/​Gemini, and that one was written by Parky and the other by Richard Beal.......

The wonderful RB has also made the source of his BIOS available, which makes it easy to modify and reassemble. It has many useful features. The “Parky” BIOS is the one that you get with the Gemini and it, too, is every bit as good as RB’s, except that the source code is not provided making it difficult to modify certain aspects of it, although a ‘patch’ area is provided for easy selection of serial/​parallel printers etc. Gemini say that the listing will be available ‘soon’.

I hope my efforts to describe the competing systems will be of help to somebody, and if asked to give an opinion, I think the best of all versions is a Nascom II fitted with the Gemini disk system, if only because the source for the alternative BIOS, SYS, is available. It makes a very worth while and powerful system. In all it must have cost 1500.00 but you name another machine with as much for less than double that price. (Sorry, we can name a couple, but none are so much fun as one you build yourself. Ed.)

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