25 Sep
2005
25 Sep
'05
9:48 a.m.
On Sun, 25 Sep 2005, Tony Duell wrote:
The distinction is correct. I should've noted that the head positioning
disk with the spiral groove in the Disk ][ mechanism is not driven by the
main motor and a clutch, but by its own stepper as you've pointed out.
--
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Apple Disk ][
drives used a similar mechanism.
Not really.. The Apple ][ head positioner (which, IIRC, was actually a
Shugart design, certainly I've seen it in a non-Apple drive, I think it
was a Shugart) had its own stepper motor. You could move the head between
tracks under program control.
The Smith Corona drive had one motor. It drove the spindle, and moved the
head. After each revolution of the disk, the head moved to the next track
inwards, when it got to the innermost track, it moved (automatically)
back to the outermost one and the sequence started again. The disk was
essentially a sequential-access thing, like a tape.