Re: CBM's CP/M, Z-80 carts for the 64

From: Gerrit Heitsch <>
Date: Thu, 20 Dec 2012 20:49:05 +0100
Message-ID: <>
On 12/20/2012 08:19 PM, Ethan Dicks wrote:
> On Thu, Dec 20, 2012 at 2:29 AM, Anders Carlsson
> <> wrote:
>> Bil Herd wrote:
>>> So while it was known that [some] 257's didn't work well
>> Am I understanding this correct that whether a C64 (or C128, or other C64
>> related computer) will operate with the CP/M Z80 cartridge to a big part is
>> due to which vendor(s) of the 257's and perhaps other 74 series chips are
>> installed in the computer? If so, those who have the cartridge and a
>> selection of machines could try to verify if it generally holds true. In the
>> rare case those chips are socketed, perhaps they could be substituted for
>> another brand if a dog slow, 40 column CP/M or other Z80 application is
>> desired to run on a C64 in the 21th century.
> I don't think those parts are socketed on any stock C-64

I have 2 C64 where the 74LS257 are in sockets and from the looks they 
came from the factory that way. Wasn't there a LS-TTL-shortage back in 
83/84? That was also the time where MOS started to make their own 'TTL', 
the infamous 77xx.

If you have a broken C64 that has one or more of those 77xx-ICs with MOS 
logo on the board, replace them first. Just had a 250407 board where the 
MOS 7709 no longer forwarded A7 from the VIC to the RAM (rather strange 
looking picture). Replaced with a proper 74LS258 and it works again.


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Received on 2012-12-20 20:00:45

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