Re: Disabling memory refresh in UltiMax mode

From: Segher Boessenkool <>
Date: Tue, 13 Dec 2011 00:36:00 +0100
Message-Id: <>
>> [206A]
>>>>> Interesting! I suspect that is an 8520 actually... Can you test  
>>>>> that?
>>>> It's soldered to a C64 mainboard and behaves like a 6526A as far as
>>>> the software goes. The 8520 doesn't have the RTC but a 24Bit timer
>>>> instead as far as I know, so I think you'd notice if you tried to
>>>> use a 8520 instead of a 6526.
>>> Not if you do not use any program that uses the TOD. And there  
>>> are not
>>> many that do. The KERNAL does not use the TOD at all.
>> Yep, exactly.
> Well, one should be able to test that by plugging a real 8520 into  
> a C64 board and then trying some software. If there is a program  
> that complains/crashes, then we know for sure that the 6526A marked  
> '206A' is not a 8520. :)

It would be rather easier to test for the difference between 8250
and 8251 directly (see if the TOD is a BCD or binary counter).

>>>> 5710 if I remember right.
>>> The 5710 from the 128DCR (and 1571CR)?
>> That's the one. Pretty obvious how they came up with that chip name,
>> heh :-)
> Well... 5xxx = CMOS, x7xx = gate arrays. See also 5717, 5719 and 5721.

Aww, but it fit so well :-)

Is the 7 in 67xx/77xx/87xx the same thing?  (I'm reading "gate array"
as "random logic", none of these devices are gate arrays).


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Received on 2011-12-13 00:00:09

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