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

From: Richard Atkinson (
Date: 2002-02-28 03:09:08

On Wed, 27 Feb 2002, Cameron Kaiser wrote:

> > As published by Richard Atkinson:
> >
> > set DDR as output
> > set DR as one
> > set DDR as input
> > wait until DR is zero

Well, I think Nicolas Welte and various others had some significant input
into the technique too...

> > However, because there are no known programs for the +4 which
> > use this feature, it might be abandoned.
> > OTOH, keeping this feature would be cool!

*ahem* I executed the program on the plus/4 at the time the technique was
discovered. It uses the only spare bit on the 7501/8501, of course. So
there is at least one "program" that uses it...

> What was this "feature" again? The faster it becomes zero, the hotter
> the chip?

Yes, I think that was it. There is a similar feature, although on a
shorter timescale, in the oscillators of the SID chip.


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