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

I have a ceramic 6526 in my CBM-II B prototype dated 0882. No revision letters or numbers at all.
 
Steve


>________________________________
> From: Segher Boessenkool <segher@kernel.crashing.org>
>To: cbm-hackers@musoftware.de 
>Sent: Sunday, December 11, 2011 6:34:15 AM
>Subject: Re: Disabling memory refresh in UltiMax mode Re: 6510 handling of $00 and $01 registers
> 
>>>> Back then the CIAs were also labled 6526R4. MOS dropped the 'R4'
>>>> later. Gives you an idea how long it took to get those working. :)
>>> 
>>> Not terribly long IMO. They shipped earlier revisions than that.
>> 
>> Those must have had some kind of bug though, or why would MOS start a new revision?
>
>There are many reasons...  Yield, timing tunings (which is also yield,
>it gives you a better sort), or indeed fixes for (perhaps critical)
>bugs.
>
>> 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).
>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).
>
>
>Segher
>
>
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