24 Sep
2005
24 Sep
'05
4:11 p.m.
On Sat, 24 Sep 2005, Chuck Guzis wrote:
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.
-tony
Portable Smith Corona word processors used a
2.8" drive that worked the
heads via a follower than ran in a spiral groove molded into a plastic
disk that was driven by the spindle motor through a clutch. Basically,
pulsing the clutch caused the head to move in a continuous spiral
pattern from the beginning of the diskette to the end. Sort of a
windshield-wiper auto-completion mechanism. You could read or write the
entire diskette (about 60K (MFM), if memory serves), but nothing less
than that. A gutless wonder if there ever was one. It was actually pretty
robust.
Apple Disk ][ drives used a similar mechanism.