80-Bus News

This issue of 80-BUS NEWS is the first for which I have written an article, so I would like to start by congratulating the editors on keeping up the best traditions of INMC NEWS and INMC80 NEWS, by publishing my contributions! In fact not a word has appeared from me for a year, but I haven’t been completely out of action during that time, as you will see.

There are four related articles in this issue, and it might help if I explain how they are tied together. First is the article on RP/M. This is the ROM operating system for Gemini computers, which has been updated. The article explains all the changes that have taken place, and how RP/M has been altered to keep up to date. The latest changes, bringing RP/M to version 2.1, have been triggered off by the introduction of the MAP 256K RAM card.

The MAP RAM is the subject of the second article, which reviews this exciting new 80-BUS card and explains how to program it.

The third article announces the latest version of SYS (15.0), which has grown considerably over the last year, and now supports almost every 80-BUS configuration you can imagine. How about a Nascom 2 fitted with a Gemini Winchester hard disk, or, perhaps Micropolis double sided floppy disks (or Pertec double sided), a standard eight inch floppy, a Gemini video card, and a megabyte of MAP RAM! With SYS it’s easy, provided a Gemini GM829 FDC controller is in use.

The fourth article, about Virtual Disks, brings together the hardware of the MAP RAM with the software of SYS. Are Virtual Disks useful or just a desperate attempt to find a use for too much RAM?

The fifth article (that surprised you didn’t it) is a review of the E.V. Beeper. It has nothing to do with the others, except that I wrote it. Happy New Year.

I noticed a strange thing when I was looking through old issues of the 80-BUS NEWS and INMC 80. Nobody has ever written anything that I can see about RP/M. There must be lots of people with RP/M in their systems, because most Gemini GM811 and GM813 computers have been supplied with it, except for those packaged with disks such as the Gemini and Quantum computers, which have special boot programs (called SIMON). One reason for this may be that many people have disk systems nowadays, so they have CP/M and are not interested in RP/M. However perhaps they give it a passing thought as it boots up their disk for them!

In case you don’t know what RP/M is, let me remind you. RP/M means ROM Program for Microcomputers. It is a 4K ROM which provides simple monitor program facilities rather like those in NAS-SYS. However the main feature of its design is that it provides a programming interface almost identical to that provided by CP/M. This means that all software developed under RP/M will run under CP/M, allowing easy migration to disks later. Also, some CP/M software, such as the Microsoft BASIC interpreter, will run under RP/M. It simply has to be loaded from tape (or from EPROM).

It is also possible to develop and test software under CP/M which is intended for use on a ROM based system using RP/M. This could be most useful where a dedicated control system is being built. For example a Gemini GM811 board could be used by itself, without video card or disks, to control equipment attached to its PIO. The sockets on the GM811 would contain RP/M, a special EPROM designed to control the system, and RAM. Also a terminal could be attached to the