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

From: Bil Herd <>
Date: Mon, 24 Dec 2012 00:41:57 -0500
Message-ID: <>
Yes there was a shortage that was created by the first wave of "handheld"
games, the little LCD based things.  Strange to think of an LS as
relatively low power but compared to regular TTL they were.

I tried to use some of the CBM versions of LS but sadly none met my
real-need timing requirements that I remember except for some real slow OC
stuff.  One time I found Russian 7406/7's in one of my designs in the
Tokyo office which I had a hard time with politically at the time. (I had
been brainwashed by the US Army that anything that supports their tech at
the time supported their war machine) I found that their version was like
1 or 2 ns slower in one direction and so wrote it off the vendor list for
that reason.   I had two rules after that as weird as it sounds; don't
feed me whale, and don't put my "cold war enemy's" chips in my computers.
The cold war was in full swing in my defense :(

-----Original Message-----
[] On Behalf Of Gerrit Heitsch
Sent: Thursday, December 20, 2012 2:49 PM
Subject: Re: CBM's CP/M, Z-80 carts for the 64

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 2012-12-24 06:00:42

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