Mythbusters

Roy J. Tellason rtellason at blazenet.net
Sun Feb 5 12:00:41 CST 2006


On Sunday 05 February 2006 02:18 am, Gordon JC Pearce wrote:
> Roy J. Tellason wrote:
> > On Saturday 04 February 2006 05:32 pm, Chuck Guzis wrote:
> >> ...and I've got a couple of 5.25" floppies where seeking to anything
> >> past about cylinder 84/42 (depending on the drive) will cause the head
> >> to jam, requiring manual intervention to free it.
> >
> > I used to see this fairly often when I was fixing commodore stuff,  the
> > head on the 1541 would get jammed to the inside,  and one would have to
> > open the case and manually move it out before the drive would work again.
>
> I'm sure I've mentioned before about the 1541 test and alignment disk we
> used to have in a workshop I used to work at...
>
> Basically it had tracks written starting too far out and progressively
> moving in until they were too far in.  They were, I believe, written
> with "worst case" patterns, and possibly a bit "quiet".  The first few
> tracks on the disk were written fairly hot so that even if the head was
> a bit out, it would still boot.
>
> What would then happen was it would step through the disk a couple of
> times, working out how "close" the head was by determining which track
> gave the least CRC errors.
>
> Then it would work out which way the head needed to be moved, wind it
> back and then smack it off the opposite end stop a few times.  Then it
> would cycle through its calibration reading again, and repeat until it
> was done.
>
> Brutal, but it worked surprisingly well.
>
> Gordon.

I don't see how it would,  since there wasn't typically anything on the inner 
end for it to smack against...

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin




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