Old Computers – why do people bother

[SillyOldDufferModerator @sillyoldduffer]

Posted by Paul H 1 on 07/02/2020 09:57:15:

It is quite refreshing to hear about the Z80 again, but does anybody remember MP/M the multi user version of CP/M. …

Certainly do, though it wasn't true multi-user. Ours, a Casu Super-C, had a single Z80 and two terminals that switched between two 64kB memory banks and shared a printer. More like two CP/M machines in one box than multi-processing. It also had a 10Mb Winchester disk, and a 10Mb Exchangeable cartridge disk. Cost £15,000, about the same as a decent 3-bed semi-detached house where I lived (not costly London or a devastated Yorkshire pit-village).

While I'm down Memory Lane, save and exit in Wordstar is control-kx

Dave

[Peter G. ShawParticipant @peterg-shaw75338]

Yes, I remember MP/M very well indeed. I was the System Manager for a Plessey MUMPS (Multi-User-Multi-Processor-System) which used MP/M as its OS, although the users saw something similar to CP/M although not called that on our system. (System Manager – glorified name for someone tasked with switching it on, doing backups, resetting it if it crashed – which initially it did frequently, although it did settle down later.)

The MUMPS had capacity for 14 users, 3 global printers & a number of local printers, plus 2 Winchester discs each having 35Mb capacity split 6Mb & 29Mb. We got it up to 11 users, some of which used some form of line extender to allow them to work at a distance and another two of which were dial-in lines, 2 global printers, one of which always behaved itself whilst you watched it, but turn your back, and the paper would jam.

Programs were Wordstar, a compiled BASIC specialist program plus a few others. The compiled BASIC program meant that we also had Mbasic, Bascom etc on the system, and I certainly wrote two Mbasic programs, one of which was in collaboration with a colleague and which netted us £500 each.

As usual, I got sent on a System Managers course after quite a few months, and was told that apparently it was possible to have dial-in lines. The lecturer was somewhat taken aback when he discovered that we had had the two dial-lines up and running for quite some time.

This was in the early 1980's, and the really ironic thing was that our group grabbed control of this system having been told that it would do what we wanted. It wouldn't so we ended up running it for other people whilst we had to scrounge a single user CP/M machine with a modem attached to do what we needed.

Peter G. Shaw

[Robert Atkinson 2Participant @robertatkinson2]

Well just to be odd I prefer PICs and a compiled basic, PicBasicPro. I started repairing equipment with Intel 4004's etc back in the mid 70's as a prt time job while still at school. Lot's of computers ofver the years. Did a lot on BBC B's, but Dragon, Oric, Sinclair Mk1, Apple II, Cromenco S100, HP 85. Apricot XI, Softy 1,2,3 and (currently), 4 PROM programmers. Used to build PC's for friends etc in the 80's and 90's but not any more.

Robert G8RPI.

[Enough!Participant @enough]

Posted by SillyOldDuffer on 06/02/2020 21:41:59:

Not sure why writing assembler for pleasure should annoy anyone,

To me the difference between writing in assembler and writing in one of the higher level languages is like building, say, a steam engine from scratch vs building it from a ready-machined kit.

….all those little registers to twiddle – what could be more fun?

[Enough!Participant @enough]

Anyone remember the days of nearly-room-sized computers surrounded by a bunch of young ladies typing away at punch-card machines?

If so, was your impression the same as mine – that the ladies became pregnant at a rate way above the national average? Always wondered about that.

[An OtherParticipant @another21905]

Time is flying faster than I thought. I still have a working ZX81, a working Oric (2nd version) and a Dragon. I also have several 4004 cpus (even when new they were useless), several 8080s, and a Z80, plus various support ICs, like 8255s etc. The Oric in particular was very good, and it was very easy to program it yourself, using assembler. I replaced the 6502 CPU with a 65C02, which has additional instructions. At the time, it was possible to buy books with a complete commented dis-assembly of the operating system, and I wrote several home-brew systems for use in it – It also has a 'real' keyboard, which is a vast improvement on the 'dead flesh' keys of the first Orics, and Sinclair Spectrums – it was a pleasure to use by the standards of the day.

The computers were bought new out of interest, because at the time I worked on a satellite tracking system which used a Honeywell tank ballistics computer to control the antenna steering, and we used three Elliott 803s for data analysis, and it was interesting to see the development of new computing techniques. To confirm one of the other posts, the Elliots did have a hard-wired bootloader, which loaded a pre-prepared 5-hole punched paper tape. If my memory is correct, they had an 18-bit word architecture, and the 803s we had a 1 kiloword magnetic core memory. I had a colleague who wrote a workable bridge playing program to run on these computers, written directly in the Elliott machine code. Puts the multiple gigabyte installations of today into perspective!

We did some (unofficial) work to use a Commodore PET as a replacement for the tank computer mentioned above. This computer used discrete components for the logic, working in non-saturating mode to obtain the necessary speed – it worked, but was a real pain to work on. It was built in a cast aluminium case about 1 metre long x 50cms square, with forced air cooling – every time you needed to change a board, it needed dismantling, change the board, then put it all back together to test it – hence the attempts to use a PET. We always wondered how they managed to hit anything when they were used in tanks. (The PET was eventually used mostly to play a golf game, because the ministry wouldn't sanction installation of the PET in place of the Honeywell – but I learned a lot doing the work.

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