Re: Disabling memory refresh in UltiMax mode Re: 6510 handling of $00 and $01 registers

From: Segher Boessenkool <>
Date: Sun, 11 Dec 2011 20:52:33 +0100
Message-Id: <>
>>> The oldest CIA I have so far is a 6526R4 with a 2383 datecode.
>> The oldest I have heard of is week 14 of 1983; those come without
>> the R4 marking. Some time in 1983 or 1984 they switched to without
>> R4 marking again (what revision is in there, I have no idea).
> Probably R4 too. From what I have seen so far MOS sometimes dropped  
> the R-number after a while for unknown reasons.

Once they had all production switched over to a new revision chip,
the revision # became irrelevant to them.

>> The last weeks of 1985 got us the 6526/S (whatever that is), and in
>> 1987 they switched to the 8521 (marked as 6526A, 216A).
> There are some that are labeled '8521R0'.


> The one I have has the datecode 4586. There are other 6526A from  
> the end of 1986 that are likely the HMOS-Version, they also show  
> the timer 'bug' and the test program lists them as '6526A'. The  
> earliest one I have in that regard is labeled '6526A  4686  
> 206A' (not '216A').

Interesting!  I suspect that is an 8520 actually...  Can you test that?

Supposedly they also did an 852x that has only the low four ports (or
the rest is not functional, anyway), i.e. the two parallel ports only;
it was called something like 5210 (I forgot the exact name, and cannot
find it anymore).


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Received on 2011-12-11 20:00:27

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