Re: 6522 vs 6526 (was Re: 6502 to 8501: new details)

From: Nicolas Welte (
Date: 2002-02-28 00:04:40

Ray Bryan wrote:
> What about the 6532 that I have seen in the Commodore printers? how do the
> the pin-outs compare to 6522 or 6526 or even the 8520 (Amiga CIA) or 8521
> (C128)? - do these match the 6821?

I don't know *how* different the pinouts are, but they are different. The 6532
is a RIOT (RAM, I/O and timer), similar, but not pin compatible to the 6530
RIOT that contains less RAM, but also a ROM.

The 6821 is a simple dual port I/O chip which is pin and register compatible
to the 6520. I think there's also the 6820 and the 6521, but I have not idea
about their capabilities.

The 6522 is a much more versatile chip (hence the name VIA) with timers and
shift registers added, and it is not compatible to any other chip. It's a very
popular chip and was used in many machines and peripherals. 

The 6526, 8520 and 8521 are all CIAs with only a few differences. All are pin
compatible, but the 8520 has a few register differences, and the 8521 seems to
be a failed 6526 replacement with some compatiblity problems. I don't know
what these problems were, but there must be a reason why only one was used per
C64 or C128, and it was later replaced by the new 6526, that has a problem
that even makes some programs crash ...

There's also the 6523 and 6525 triport interface adaptors: pin and register
compatible, but the 6525 has more registers and functions.


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