27 Nov
2005
27 Nov
'05
12:03 a.m.
Micropolis drives were 30 ms. track-to-track. I
believe they used a 4-step
I am not disputing that the Micropolis drives were slow. What I am
questioning is whether that was solely due to the use of a leadscrew.
per track scheme. The last Micropolis 5.25"
drive (with buffered seek) I
Interesting, I've never seen a floppy drive with buffered seeks, and
since there's no seek-complete pin on the interface connector, I don't
see how it could really work. Every floppy controller I've ever seen
sends the step pulses at a constant rate, which would have to be slow
enough for the worst case.
have has a closed-loop tach belt-drive spindle motor.
I've never verified
it, but I suspect that with longer seeks, the stepping rate is sped up
considerably. I recall fooling with the step rate on a paper-feed motor on
That's the normal idea of buffered seeks.
a printer and discovering that once you've
established direction, you can
crank the stepping rate pretty far up. Try it before things really get
moving and you're likely to find yourself stepping backwards.
Sure... I remember the Sanders dot matrix printers that ramped up (and
down) the step rate of the carriage feed stepper and sent the printhead
pulses at just the right times to put the dots in the right places.
When the taut-band positionier 5.25" drives came
out, our drive specialist
did some tests using MPI and Tandon taut-band positioners and declared that
they were good enough and much faster than the Micropolis. So we used
both for a time, but eventually settled on Tandon, albeit with our own
drive electronics--he didn't think much of the Tandon PCBs.
IIRC, HP used Tandon drives at one point with their own PCBs. Well, they
had HP part numbers, and were gold-plated like most HP PCBs of the
period, but they seem to have much the same layout as the normal Tandon
PCB...
-tony