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Commodore PC-1 CGA compatibility

MindWalker

Experienced Member
Joined
Jul 23, 2019
Messages
68
Location
Helsinki - Finland
Hi,

I have a Commodore PC-1, which I have upgraded to 640k of RAM.

Some games that I’ve tried to run, and I *presumed* should run on the machine (like Arkanoid, Prince of Persia etc) complain that they cannot detect CGA hardware and refuse to run. Arkanoid II complains that it can’t detect any of the graphic adapter options (CGA, Hercules), but it lets you manually pick it anyway - and the game runs in CGA. Also Planet X3 works in CGA (and of course in the special Plantronics mode, which is cool!), and for example AlleyCat so I believe the machine should indeed have a working CGA graphics adapter.

There was one comment in YouTube (RetroSpector78's repair of the PC1) that says: "To run a lot of CGA games we had to run a small TSR program and then the CGA games would run fine. I don't remember the name of it but it was part of the disks you got with the machine”. Does this sound familiar to anybody, what might this program might have been?

I have set the DIP switches to 80 column, colour, CGA mode. I am running MS-DOS 3.20 (nothing special or graphics related in autoexec.bat or config.sys, should there be?), and CheckIT identifies the video adapter as CGA (at B800h, 16K of video RAM). I am using a Monotech EternalCRT with a modern VGA display.
 
Huh. I had a Commodore Colt briefly back in the day, which I think is pretty much the same machine, but don’t recall having issues like that.
 
AFAIK, the Commodore Colt was a rebadged PC10-III or PC20-III. The PC-1 is somewhat different.
I suspect that the TSR they mentioned was a primitive fix for some missing or buggy BIOS routine.

Planet X3, including the Plantronics code, does not do any CGA hardware detection. I know that for a fact.
 
Yeah I was thinking that the issue appears to be some check (for CGA adapter presence) that fails due to some difference in... architecture perhaps. As many CGA games (that don't bother to run any checks) appear to work.

I was hoping that this would be an issue not just with the PC-1 but something more generic (thus making the fixes perhaps easier to find).

Forgot to mention that I've upgraded the BIOS to the newest 1.2 (that I was able to find online).

Also if anyone have original PC-1 specific system disks available, that would be great! Just in case there was something special included there (I am currently using PC10-era Commodore branded MS-DOS 3.20 disks)
 
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