Uh, I beg to differ about the Victor 9000 being the
first computer to use
variable speed disk drives, as my CBM 2040 dual drive unit from 1979 does
this.
No it doesn't (or at least the 8050 doesn't, and nor does the 1541 - I
have service manuals for both of them)
The disk turns at a constant speed. What changes is the speed of the data
clock. The bits are sent faster for the outside tracks, so it can fit more
sectors on said tracks.
I never really saw the point of variable-speed drives. Changing the data
clock is a lot easier, and probably faster (getting the spindle
up-to-speed and locked at that speed takes considerable time).
That's how it gets 21 sectors on tracks 1 to 17, 20 sectors on tracks 18
to 24, 18 sectors on tracks 24 to 30, and 17 sectors on tracks 31 to 35.
AFAIK, all PET-era CBM drives do this, and the 1540 and 1541 drives do as
well.
Doug Spence
ds_spenc(a)alcor.concordia.ca
--
-tony
ard12(a)eng.cam.ac.uk
The gates in my computer are AND,OR and NOT, not Bill