Re: CP/M, 64C, C64

From: Petri Andras (
Date: 2005-04-14 14:31:49

On Thu, 14 Apr 2005, Glenn Holmer wrote:

> I picked up a CP/M cartridge on eBay, but was disappointed to find that
> it seemed broken when I put it to my 64C (screen corruption, etc.).  But
> just on a whim, I switched out the 64C for a C64, and the cartridge
> works beautifully.  Are there any differences between the two that might
> cause this?  I am using a heavy duty power supply (the kind that came
> with the REU), and the 64C works beautifully with everything else
> (including SuperCPU).

Dear Glenn,

the C64 CP/M card has several serious design flaws (it was discussed on
this list around March 2000; maybe Ruud Baltissen can be asked about the
gory technical details), so it is not supposed to work reliably at all on
any C64 version ;-)

One of the flaws make it so excessively sensitive to the timing of the CPU
bus signals that sometimes it keeps crashing immediately after you've
powered the C64 on, but starts to work after 5-10 minutes (when the chips
within the C64 case have warmed up a bit). So consider yourself very lucky
that you could make that big black blob work...

Anyway, as the CP/M cartridge was introduced at the end of 1982, the debut
year of the C64 (and dropped in deep silence a few months later), it seems
to tolerate the old "Brotkasten" version a bit better.


Andras Petri

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