t.gardner at computer.org
Sat Jan 24 16:07:51 CST 2015
FWIW, the Seagate ST-4096 apparently used an unused pin in the data cable to place the drive in a Recovery Mode where the step and direction lines would then be used to microstep around the then current track. There are several unused or rarely used pins in the ST-506/412 interface that could have been repurposed to enable microstepping. AFAIK, there was no standard.
From: Tom Watson [mailto:tsw-cc at johana.com]
Sent: Friday, January 23, 2015 7:58 PM
To: cctech at classiccmp.org
Subject: Re: Maxtor XT-2190
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".
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