Re: Could you make a 'new', 'better' computer from the C64 just by reprogramming the PLA?

From: Francesco Messineo <francesco.messineo_at_gmail.com>
Date: Thu, 4 Nov 2021 16:43:50 +0100
Message-ID: <CAESs-_wkhNYf0uRgWBf40GQbgioryUtXXZhXx4su8b3XVhAfKA_at_mail.gmail.com>
On Thu, Nov 4, 2021 at 4:31 PM Jim Brain <brain_at_jbrain.com> wrote:
>
> I'm surprised they didn't use their
> internal 65XX RAM option (6550?)

basically 6550 were already an "old" thing by 1979.
Even the original 2001 motherboard had at least two revisions that
used 2114 instead of 6550.
MOS made its own 2114 too, but in my repair records, these are failing
a bit more often than other brands' ones.
6550 tend to be a bit too unreliable too. I have a collection of 16
failed ones from the repaired 2001 of the last few years.
My own 2001 alone "donated" 10 of them to the "failed collection".
However the 18 x 6550 it has now are still working today.
Using a 6550 instead of a 2114 for color ram on the C64 would have
been pointless anyway, since the big differences are just
the great flexibility in the CE choices (5 different CEs on 6550) vs.
one /CE on the 2114 and the bigger size of the 6550 (22 dip 400 mils).

Frank IZ8DWF
Received on 2021-11-04 17:02:38

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