1 Jun
2008
1 Jun
'08
7:21 p.m.
Grumply Ol' Fred wrote:
And mine.
Although it is prob'ly irrelevant to this
particular problem, IIRC,
buffered seek was one of the major differences between the ST506 and ST412
intrerfaces.
That's my recollection as well.
On early drives, the point of buffered seek was to allow the electronics
on the drive to use an acceleration profile specifically tailored to
the stepper motor and actuator mass of the drive. Before buffered
seek, the time to seek n tracks was exactly n times the track-to-track
time. Buffered seek improved the seek performance considerably for
longer seeks.
The SA4000 (14" Winchester) has a rather odd seek specification. It
supports buffered seeks -- sort of. You can either send it step pulses so
slowly that it steps one track at a time, or you can send it a burst of
step pulses so faster that it buffers the lot and then does the seek. But
if you send step pulses at an intermediate rate, it'll miscount them
(there is one up/down counter clocked both by the step pulse and the head
movement logic, and the logic around that is 'minimal'...) and the heads
won't end up on the cylinder you expect.
-tony