wales@valeria.cs.ucla.edu (04/01/89)
A few months ago, I installed a high-density (1.44Mb) 3.5" diskette
drive in my Taiwanese turbo XT clone.
For the most part, it works just fine. Despite some warnings about
unreliability of such drives in PC's and XT's, I have had almost no
problems. The drive passes Fastback Plus's "High DMA" test without
errors.
I have some Sony disks, and some Maxell disks. When the system has
been on for a long time and has warmed up, a few of my disks (I think
they're all Sonys, but one or two might be Maxells) develop bad spots
in the last few cylinders. The problem occurs *only* on the last two
or three cylinders of a diskette. Frequently, only Track 79, Head 1
is affected.
If I clean the drive with a "wet" (alcohol/freon) cleaning diskette,
the bad spots go away (e.g., the diskette formats without errors) --
but after a couple of minutes the problem returns. The surface of the
cleaning diskette is *not* visibly dirty after cleaning.
*NOT ALL* of my diskettes act this way. For example, I have two spare
Sonys which give me trouble, but three spare Maxells that format 100%
error-free even when one of the Sonys has just shown a bad spot.
When my system is relatively cold (hasn't been on for very long), I
rarely if ever have any problems. Only when the system is warmed up
does it act up.
I have installed an internal fan blowing at my floppy controller (as
well as my hard disk), but this doesn't seem to make any difference.
Since my system is mounted vertically ("tower" configuration), I also
drilled some extra holes on the bottom near the disks and mounted a fan
there to blow warm air *out* of the case; this also doesn't seem to
matter. (I'm planning to try reversing this fan to suck air into the
top of the case, but I haven't gotten around to doing this yet.)
I can see three possibilities, but no real way to choose among them:
(1) The diskettes in question are genuinely marginal and experience
problems when the drive is warm. This might explain why only some
diskettes exhibit problems -- and virtually all of them are of a
single make.
(2) Something is going flaky in my diskette drive when it warms up;
cleaning the heads cools them briefly, causing the problem to go
away (but only for a while).
(3) My floppy controller is flaky (except this wouldn't seem to explain
why cleaning the drive heads "fixes" the problem for a while).
Does anyone out there have any ideas or suggestions?
-- Rich Wales // UCLA Computer Science Department // +1 (213) 825-5683
3531 Boelter Hall // Los Angeles, California 90024-1596 // USA
wales@CS.UCLA.EDU ...!(uunet,ucbvax,rutgers)!cs.ucla.edu!wales
"I couldn't read it because my parents forgot to pay the gravity bill."