Re: VIC-II DRAM refresh

From: Francesco Messineo <>
Date: Fri, 14 Oct 2016 19:16:12 +0200
Message-ID: <>
On Fri, Oct 14, 2016 at 5:12 PM, Michał Pleban <> wrote:
> Hello!
> Francesco Messineo wrote:
>> isn't the 8520 a 6526A (or B?) but made with a different process? I
>> could use the 8520 in place of the 6526 with no problems once.
> No. The 8520 has a different TOD timer, if you use it in the C64 the
> programs which rely on it will not work (or will display incorrect
> time). Also the TI$ variable in BASIC relies in the TOD in one of the
> CIAs so it will not work too.

yes, it was 8521 then. I'm sure at one point there was the 85xx
version of the 6526.
Too many numbers to remember correctly. I usually check the documents
and/or the network knowledge before doing substitutions. I know there
was a TOD-less or TOD-different version
of the 6526, it's just hard to remember all those MOS numbers.
Why they couldn't use consistent numbering is something I always wondered.
Even with TTL-compatible logic, they could invent any consistent
numbering, like XXYY257
instead of 7708 and XXYY258 instead of 7709...
For example, their 74LS245 equivalent was following that golden rule,
so at one point they decided to "go insane" on numbering.


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Received on 2016-10-14 18:00:02

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