CP/M 3.1

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CP/M 3.1

Post by Coeus » Mon Jun 18, 2018 10:49 am

In the documentation for YAZE-AG it mentions making changes to enable CP/M 3.1 to be run but actually ships with ZPM3N10, a free replacement. Looking through the network of CP/M related pages including JGH's CP/M page on mdfs.net and The Unofficial CP/M Web site, I can find no other mention of it.

I do find CP/M+ mentioned, aka. CP/M 3 but looking at the Digital Research source from The Unofficial CP/M Web site that appears to be version 3.0.

Does anyone know anything more about it? Is it published anywhere? Was it every widely used? What are the differences from 3.0?

And, while we're at it, was any version of 3 widely used or much software written for it?

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Re: CP/M 3.1

Post by scruss » Sun Jul 22, 2018 5:21 pm

From what I remember, it was a minor bugfix/feature on 3.0. It may have added easier user configuration: CP/M 3 added rudimentary system-wide support for terminals. CP/M 3.1 was shipped with the Amstrad CPC6128, Amstrad PCW range, ZX Spectrum +3 and the Commodore 128.

I recall it was more often called CP/M+ that 3.x. Features it added over 2.2 included:
  • date stamps - CP/M 2 had no idea of real-time clocks, and any support for dating files was done as a hack
  • banked memory - borrowed from MP/M, this allowed an Amstrad CPC6128 to have a 61 KB TPA. This was kind of a neat trick, as the 6128 ate 16 KB of its main RAM for the screen
  • encryption - file encryption, in name only
  • better GSX integration. GSX was DR's vector business graphic extension
  • terminal/I/O customization - the old way of supporting different terminal types under CP/M 2.2 was patching binaries. This was likely valuable for the PCW and +3, as they had non-standard terminal sizes.
CP/M+ is a little harder to implement than 2.2, as you need to go off and look for additional CPM3.SYS file while booting.

As for software, a lot of the CP/M+ specific packages came out of the UK: Arnor's Protext (originally on ROM for the CPC, much expanded for CP/M+) and Maxam II development system, and also Locomotive's Mallard BASIC, a rather nifty business basic. I keep toying with the idea of getting CP/M+ running on my Zeta 2, but that would be a ton of work just to run Protext.

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