On Mon, Apr 17, 2000 at 11:26:08AM +0100, Frank Peelo mentioned:
> > ...
> > As for the 800Kb disks, the Mac uses a variable speed drive in order to
> > increase the capacity of the disk - slows down when it moves to outer
> > thus enabling it to write more. Cute idea - got 80K more than the PC did
> > (Amiga gets more :)
>> Sounds like the scheme ACT Sirius used (with DOS 1.25 or CP/M86) to get 620K
> on a single-sided 5.25" disc (the PC type discs, not the AT version) while
> the PC was getting 180K. Slow as anything and incompatible with everything,
> does the Mac still use it?
I thought one of the best stories that Alan Cox told was that one of the
older/cheaper Macs was built in such away, that to save money, the 800k
floppy driver was built without the little DSP (or whatever) to generate
the stepper motor input frequency (which would go up, when you were
reading the outside of the disk, so that it would spin faster).
Anyway, to get around this, they wired the sound card to the input of the
floppy drive, so that it would do the job. The effect ? If you were
playing a sound, and then tryed to read the floppy drive, the sound would
shut off, and the floppy driver would tell the soundcard to play a
high-pitched sound, if it was reading the outside of the disc, and a
low-pitched sound if it was reading the inside of the disc.
Mad. The things computer makes do, to save 30p or so.
"The fool must be beaten with a stick, for an intelligent person
the merest hint is sufficient" -- Zen Master Greg
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