Date   : Tue, 09 Sep 1986 19:58:31 GMT
From   : Dave Haynie <daveh%cbmvax.cbm.uucp@BRL.ARPA>
Subject: Re: Z80 Cartridge for C64... HELP!!!

> Xref: cbmvax net.micro.cbm:455 net.micro.cpm:598
> 
> Hi all!
> I seem to be having some trouble with the Z80 cartridge I purchased recently
> for my C-64.  It doesn't want to boot up on my machine.  I did find some
> information that the Z80 will not work on the later models of the C-64,
> namely, the 3rd and 4th models.
> Does anybody out there have any information on how to make the Z80 work on
> these later models?  It would be a great help.
>      
> Thanks in advance,
>      
> Bill Myers
> Penn State/York
> OP4@PSUVMA.BITNET
>      

You've found a classic problem , which is waht resulted in the Z-80 card
being discontinued.  The original card worked fine on the C64 that it was
designed for.  That machine used a Revision 5 (as I recall) VIC chip.
Later on, the VIC was revised to cure a problem it had with sparkling
characters.  That impacted on total system timing, but no effort was made
to fix the CP/M card.  The result is that if you have a system with a
REV 7 or 8 VIC, you have less than about 50% chance of the CP/M card
working.

-- 
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Dave Haynie    {caip,ihnp4,allegra,seismo}!cbmvax!daveh

       "I gained nothing at all from Supreme Enlightenment, and
        for that very reason it is called Supreme Enlightenment."
                                                       -Gotama Buddha

       These opinions are my own, though for a small fee they be yours too.
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