Running CP/M on the C128
celso.io
celso.io
The posted article mentions how slow C128 CP/M when compared to comparable machines, but I really didn't notice. It ran quickly enough for my needs.
This hit me with so much nostalgia. Different parts of the world - same experience.
There was a small Amiga shop on 18 de Julio Avenue and I once took a friend from Brazil there and he was mesmerised; I couldn't get us out of there. I remember the owner was called Juan; he was a nice chap and we talked all afternoon.
In Brazil we had to make do with mostly clones of PCs and Apple IIs (and, later, MSX). Sadly, computer imports were very restricted in order to protect a local industry which was considered strategic. The policy was somewhat successful in the end, but not to the extent the government - a military dictatorship - intended, which was to bring about a completely local industry. There were few locally developed architectures, most based on imported components, and the bulk of the industry centered on clones with minor improvements (such as better peripherals, higher integration) in order to remain compatible with the existing software base.
And when push came to shove with Unitron's Mac, Brazil gave precedence to its orange exports. So I would classify it as a half-hearted attempt at industrial policy.
95% of C128s spent 95% of their time in C64 mode.
>I did have a CP/M floppy, but I only booted it once or twice, had no clue what to do with it, and forgot about it quickly.
If 1% of C128 users ever used the bundled CP/M disk for more than what you did—boot it to see what it's like—I'd be surprised. 1985 was just too late to expect people to buy a new computer to run CP/M.
It's how I got to play a bunch of Infocom games and some other interesting stuff. But CP/M was boring and I only ever saw dad use it for word processing a few times. Most of my time was spent messing with games, getting S.A.M. to swear, and digging through the C128 BASIC manual to figure out how write programs to make pictures and play music.
edit: also use The Print Shop to create banners and use up all our printer paper, much to the chagrin of the aforementioned father.
When IBM first developed the PC they needed an OS. At first they tried to license CP/M from Digital Research since it already existed with many applications available. But when DR fumbled the business negotiations, Microsoft stepped in and offered IBM favorable terms for MS-DOS. It wasn't exactly compatible with CP/M, but close enough that the transition was easy for users and developers.
https://www.cringely.com/2013/02/28/accidental-empires-chapt...
https://en.wikipedia.org/wiki/File_Control_Block
This block would contain the command-line arguments, and have space for working with files (via FindFirst and FindNext), using the same globbing patterns as CP/M supported.
Of course things changed when MS-DOS got support for subdirectories, and later int21 functions expanded filesystem support. Later still .exe files became more dominant as they could be larger than 64k (minus PSP).
It just didn't sell well for Commodore compared to the Commodore 64 and the Amiga. As a replacement for the Commodore 64, it was a sales disappointment. Most other manufacturers would have been thrilled with a failure like that, however.
That said, perhaps more accurate would be to say that using CP/M to position the C128 that was didn't help much - even of the people who bought a C128, most never used CP/M. Though to some it might have been what allowed them to convince parents it was a "serious computer".
I still have a (printed on dead trees!) manual for Coherent 3.2 (286 version, circa 1990-91) kicking around. Ran multiuser (login via tty or virtual terminals on the console) in 640Mb of RAM, off a 10Mb fully installed setup. If I remember correctly you were limited to 64Kb code & 64Kb data per process, though ... (Coherent 4.0 removed the addressing limit).
In particular Shiraz Shivji, who was the main designer of the ST, was part of the S900 project.
Pretty sure the S900 was effectively dead before the C128 project was even started.
And in any case the S900 was a monochrome business computer, aimed at the productivity market -- a segment Commodore later targeted with PC compatibles instead.
The C128 was targeted at consumers who wanted to run C64 games.
- Any pointers?
PS: Great post, by the way - I was also a “kid pilgrim” to the computer store. ;)
The Z80 and the 6502 (well, 8502 actually) CPUs share the same bus, and so there can only be one CPU running at one point in time. However afaik in CP/M and Z80 mode there are some I/O functions for the keyboard etc that halt the Z80, switch to the 8502, do what they do, and then switch back.
I'm not sure if you can somehow programmatically switch from the Z80 to the 8502 and back, though. I suspect not.
(If you have a floppy, though, the 6502 in the disk drive would still be available, and run in parallel, but the disk drive was both severely memory constrained and of course limited to the serial bus.