Re: Fwd: Re:6526-8521(8520)Differences 6510 and 8500 differences (fwd)

From: Richard Atkinson (
Date: 2000-07-31 19:26:39

On Mon, 31 Jul 2000, Ray Bryan wrote:

> Is anyone testing the differences between the CIAs 6526 (orA)(C64) 
> and 8521 (C128 and some C64c's) or 8520 Amiga 500/1000/2000/3000 -- 
> that address, $DExx, is in the CIA.  What about differences between 
> 8501(7501) and 8502 and 8500?

Between 6526 and 8521 we are not sure, yet. I can't even remember which
way round they are installed - one for the keyboard and the other for the
user port. This will probably get investigated in due course.

8520 has clear differences in the software model (no TOD clock) and does
not concern us here. 8500, 8501 and 8502 have pinout and software model
differences, so again it is not difficult to detect them, although since
each is used in a very different type of Commodore machine you wouldn't
need to detect them.

7501 vs 8501 is more interesting. This case is like 6510 vs 8500 except
that the two are fabricated in more similar technologies; HMOS-I and
HMOS-II. I am not aware of HMOS-I machines outside of America, so our US
friends will have to help us out on this matter. Who has a 7501 machine?


Richard Atkinson
Software Engineer
Tenison Technology EDA Ltd

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