From: dnichols@ceilidh.beartrack.com (Don Nichols (DoN.))
Subject: Re: Marching Boxes
Organization: D and D Data, Vienna Virginia
Date: Fri, 24 Jul 1992 23:20:47 GMT

In article <Brv1EL.F7J@wrs.com> gak@wrs.com writes:
>I didn't see anything in the FAQ about the infamous "marching boxes"
>problem, so here goes...
>
>I've had the problem once in a great while, and I could always fix it
>by cycling the power, but now it seems to be permanent.  Cycling the
>power hasn't helped.  I ran the Hard Disk diagnostics, and it doesn't
>seem to recognize the disk at all.  I suspected "stiction", and I tried
>the usual remedy, but no dice.

	Seems a reasonable suspicion.  Is the room quiet enough for you to
hear whether the drive spins up?  If you hear the drive spin up, stiction is
not the problem.  However, if it doesn't spin up it is almost certainly
stiction.  With continued use, the disk with stiction problems gets worse
and worse, requiring more and more violent means to counteract it.  It's not
clear whether you have a 7300 or a 3B1, so I'll mention that with the drives
shipped with the 7300 (which are not self-parking), it helps to park the
heads prior to powerdown.  (To make this easier, and reduce wear and tear on
the diagnostics floppy, you can make a copy of the diagnostics kernel (which
is probably appearing under two entries in the directory listing of the
floppy, one is /unix, and the other is something like /s4diag or /s4test.
Anyway, copy it to the hard disk in some directory other than the root
directory, but make it a short path.  I use /kern as my directory, and have
the diagnostic kernel (aw well as others, like the tape one) there, and use
the modiifed verbose loader.  When it boots, it waits a while asking what
drive to boot from, and afterwards what file to boot.  Using this you can
specify /kern/s4diag as the boot kernel, and use that to park the
heads.	 With the heads parked, they are at a minimum radius, which requires
a minimum torque to break the stiction.

	Still, the best advice is to replace the drive in question.

>Is there a standard quick-fix for this problem, or are there many
>unrelated causes?  I'm ready to open it up and start digging, but I'd
>sure appreciate any clues as to what I should be looking for...

	While the box is open, it wouldn't hurt to check for signs of
overheating in the plastic connector on the ribbon cable which connects to
the power supply.  They will be evident with browning of the plastic in the
region of the pins that are overheating.  If you have this problem, I would
expect you would have been seeing lots of HDERRs, so you probably don't have
this problem.

	You can attempt to turn the flywheel for the disk drive by hand, if
it is accessable.  You may need to remove the pc-board to do this.  Don't
turn it very far, but you should feel a sudden release of tension as the
heads break free.  This is a last-ditch action, because it is as likely to
damage the disk surface as not.  At this point, you should have on hand
enough floppys to back up everything, and have the distribution floppys on
hand to start a rebuild on the replacement disk, because with the old drive,
things will only get worse.  Anything that you don't back up, and don't have
on distribution disks or other media, you should plan a wake for.

	Good Luck
		DoN.
-- 
Donald Nichols (DoN.)     | Voice (Days): (703) 704-2280 (Eves): (703) 938-4564
D&D Data                  |  Email: <dnichols@ceilidh.beartrack.com>
I said it - no one else   |         <dnichols@ceilidh.aes.com>
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