The discussion about servos on the XT2190 prompted me to turn on a machine (Altos ACS
68000) that I have with one of these nice drives in it.? The initial sounds of the drive
is it re-calibrating using a stepping sequence.? This may be done by the drive controller
to find track zero, or the drive itself (I really don't know).? Since the stepping
(and subsequent servo lock) happens at a low frequency, it is the sound you hear.?
Sometimes it takes a couple of times to get its act together, but it works well.? This was
a machine that had been off for a bunch of years (over 10?) and it came back to life
nicely.? I couldn't say much about the terminal I had attached as the dust that had
accumulated made some keys not function so well, but I'll take some canned air and
"blow it out" to get it working well.
I note that the MFM interface does not have any "microstep" capability, only a
simple step function.? I believe that the SMD interface did (it has been a few years, I
never used it in my work), and the ESDI might (I never worked with that one).
Soon I'll get the MFM drive simulator working and go "solid state".