EX2000 Floppy Drive Tester

Chuck Guzis cclist at sydex.com
Sat Aug 12 16:36:57 CDT 2006

On 8/12/2006 at 5:07 PM Dave Dunfield wrote:

>What exactly does the "drive excerciser" do which comes in handy?  -- I've
>got some diagnostics and drive test tools built into ImageDisk which I
>very useful, and I'd be happy to add any other such functions that folks 
> need (provided of course that it can be done with the PC hardware).

Doing a good job on drive alignment generally requires an alignment
diskette and a 'scope.   However, there were alignment diskettes produced
with tracks that were skewed across the width of a track.  The idea being
that you listed the sectors that could be read and that would tell you
approximately how far off alignment you were.

Back in the belt-drive DC motor days, things like Instantaneous Speed
Variation were important, but you don't see that being tested on the
direct-drive models now.  Just a simple averaged speed check is adequate on
modern drives.

Leadscrew positioners (or even the cam-and-follower type in the SA400)
sometimes display backlash, which can be checked with an alignment diskette
by approaching the same track from the inside and the outside tracks.
Taut-band positioners generally don't show much backlash.  But in the bad
old days, recovery from a data error could took the form of:

1.  Re-read in place 3 trimes
2.  Recalibrate (seek to track zero), seek to track and re-read
3.  Recalibrate, seek past the track and then step backwards and re-read
4.  Recalibrate, single-step to the track and re-read.

What the first accomplishes is pretty obvious.  The second attempts to make
sure that the head position hasn't drifted and also tries to knock any
schmutz loose from the head.  The third attempts to compensate for backlash
in the positioner.  The fourth tries to anticipate a slugglish positioner


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