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From: maurice@sol6.cs.monash.edu.au (Maurice David Castro)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Auto park disc drives.
Message-ID: <4498@bruce.cs.monash.OZ.AU>
Date: 26 Jun 91 12:54:31 GMT
References: <1991Jun25.122949.13109@news.larc.nasa.gov>
Sender: root@bruce.cs.monash.OZ.AU
Lines: 35

From article <1991Jun25.122949.13109@news.larc.nasa.gov>, by burton@asdsun.larc.nasa.gov (John Burton):
> I'm not sure of the technical reason *why* head parking software would
> damage an autopark drive, but I've *seen* it happen (not a pretty sight :-)
> Most (not just conner) autopark drives (primarily voice coil) come with this
> warning...so there must be some reason for it...

I can not comment on the modern autopark drives, but a few years back, when
286s were young, there was a warning not to use XT harddisk parking programs
with certain AT harddisk units. No explanation was offered at the time for
the behaviour, however, the following is a suggestion:

* IBM harddisks are a mess when it comes to parking zones, an AT bios lists
  many different tracks for parking or shipping the disk. XT programs do not
  access the bios list and hence do not know where to park the drive.

As to the current problem the following is a possibility:

* One parking program basically seeks the last track on the disk and 
  parks over that. This works on some drives, however, this method would
  not actually place the heads in the right place for a voice coil self
  parking drive. 

If anyone knows the real story ...

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Maurice Castro                 |  "In hardware engineering, Ohm's
maurice@bruce.cs.monash.edu.au |   law and Maxwell's equations pale
                               |   in importance and influence next
                               |   to Murphy's Law" Gordon Bell
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Maurice Castro                 |  "In hardware engineering, Ohm's
maurice@bruce.cs.monash.edu.au |   law and Maxwell's equations pale
                               |   in importance and influence next