Re: 6502 illegal opcodes questions

[pausch@saaf.se (Paul Schlyter)]

In article <e4kl5u$5qq$1@news.lrz-muenchen.de>,
Rainer Buchty <buchty@atbode100.lrr.in.tum.de> wrote:

> In article <qh1wuqmoqz.fsf@ruckus.brouhaha.com>,
>  Eric Smith <eric@brouhaha.com> writes:
> |> buchty@atbode100.lrr.in.tum.de (Rainer Buchty) writes:
> |> > There are quite some "it wouldn't work otherwise" examples, though,
> |> > which require those undocumented opcodes to meet strict timing.
> |> 
> |> Such as?
> 
> IIRC the S-JiffyDOS patch uses illegal opcodes to speed up GCR decoding.
> (Jochen, are you reading here and can comment?)

That can also be done without illegal opcodes.  The Apple Pascal RWTS
did it, and was able to read all sectors of a floppy on one revolution
of the disk -- oncluding GCR decoding on-the-fly.

 
> And I'm sure quite some demos contain illegal opcodes to either make
> effects possible at all or get the max out of the raster timing.
> 
> Rainer

Only demos?  Not sharp applications?  :-)

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