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From: ashok@softart.UUCP (Ashok C. Patel)
Newsgroups: net.micro.pc
Subject: Re: 1.2meg <-> 360k
Message-ID: <13@softart.UUCP>
Date: Sat, 1-Nov-86 01:14:55 EST
Article-I.D.: softart.13
Posted: Sat Nov  1 01:14:55 1986
Date-Received: Mon, 3-Nov-86 21:09:37 EST
References: <3667@sdcc3.ucsd.EDU>
Organization: Softart Microsystems Inc., Waterloo Ont. Canada
Lines: 39

>   When I recently acquired a Tandy 3000 someone suggested I get one of each
> kind of drive.  They gave essentially the same warning about track width.
> I did not follow the advice -- I got two 1.2 meg drives even though I need to
> exchange data with an older machine using 360k.  I found it is fairly easy to
> avoid having both machines write to the same disk -- but the recent postings
> aroused my curiosity.  I ran some tests using Forth (so I could be sure that the
> same tracks were being used by both machines).  I could not produce any problems
> no matter what.

You got lucky.  That's all.  Whenever a track is written to the disk, there is
no doubt some "magnetic leakage" written around where the track should be.  If
both drives are aligned just so *AND* the data separater in your controller was
properly tuned, the weaker part of the 360k track (after being overwritten)
would not be read and everything would look OK.  If, however, your 1.2Meg and
360K drives were skewed in opposite directions, the "strong" signal written
by the 1.2Meg drive would come in even weaker and that's where the trouble
begins.  I too have an AT and XT and for the first 6 months or so, I could
transfer disks with no problem.  After that, the drives became sufficiently
skewed (It doesn't take much) and I could no longer read the disks reliably.
I ended up buying the extra 360K drive for the AT.

> I can only report that there must be something wrong with a
> theory whose predictions are not supported by experiment.
> 						     --J Wavrik
> 							UCSD

It may be just that someone has oversimplified the theory for better
understanding by those not "in the know" about such things.  IBM would not
have posted warnings time and time again (on *EVERY* scrap of paper that they
publish about the 1.2Meg drives) if there was not indeed a promblem!  It just
isn't cost effective!

I hope that this ends the discussion about what should have been a three or
four message discussion!


Ashok C. Patel
Softart Microsystems Inc.
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