Re: Fast GCR decoding?

From: David Wood (
Date: 2005-11-11 21:22:28

I know its offtopic and we all love to hate apple, but I read some
interesting information in a hardware reference book.  There's a GCR nybble
exactly every 32 cycles.  There's no byte ready line or other hint that a
nybble was read.  Just read, and -exactly- 32 cycles later, read again or
miss a nybble. :)

The 1541 uses a variable bit clock, so it can vary, but the smallest sector
count matches the evil system at 16/track, so it's probably not far off.  ;-)


On Fri, 11 Nov 2005 wrote:

> On 2005-11-08, at 10:33, MagerValp wrote:
> >
> > No, there aren't enough cycles to decode to nybbles in realtime,
> Could you remind me how many of them are there in the worst case?
> --
> Apple products look like they come from designers that Ikea wish they
> could afford. - Ian Brogan
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