Re: C64C case production molds resurfaced

From: Spiro Trikaliotis <ml-cbmhackers_at_trikaliotis.net>
Date: Wed, 4 Mar 2015 21:11:40 +0100
Message-ID: <20150304201140.GA25836@hermes.local.trikaliotis.net>
Hello,

* On Wed, Mar 04, 2015 at 09:03:56PM +0100 silverdr@wfmh.org.pl wrote:
> On 2015-03-04 20:47, Gerrit Heitsch wrote:

> >The 8520 had a normal timer instead of the RTC the 6526 had. That's
> >about it, you can use a 8520 in a C64 if the software doesn't use the RTC.
> 
> You mean the TOD? I'd have to re-check.

Exactly, that's the only difference between 8520 and 8521. The TOD in
the 8520 just counts, while the 8521 (and 6526) output the result in
BCD.

In both cases, the TOD has exactly 24 hours.
 
> And what if it is a 6526A? Or are all 6526As basically 8521s?

It seems so. At least, the 6526A all have the difference that their
timer fires one clock too early w.r.t. the "normal" 6526. Although I am
currently not exactly sure if the 6526 is too late, or the 6526A is too
early with respect to the documentation.

One example for a program that does not work: The trace command of SMON
(from 64'er) relies on the 6526, and it will fail with the 6526A / 8521.

Regards,
Spiro.

-- 
Spiro R. Trikaliotis
http://www.trikaliotis.net/

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