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

From: Gerrit Heitsch <>
Date: Sun, 11 Dec 2011 13:12:57 +0100
Message-ID: <>
On 12/11/2011 12:34 PM, Segher Boessenkool wrote:
>> 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.

> 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').


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Received on 2011-12-11 13:00:04

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