Path: utzoo!utgpu!attcan!uunet!dalcs!lane
From: lane@dalcs.UUCP (John Wright/Dr. Pat Lane)
Newsgroups: comp.sys.ibm.pc
Subject: Re: More ? re Formatting and writing 360K diskettes with 1.2M drive.
Message-ID: <2975@dalcs.UUCP>
Date: 15 Aug 88 06:37:44 GMT
References: <11069@cgl.ucsf.EDU> <2977@nicmad.UUCP> <6239@chinet.chi.il.us>
Reply-To: lane@dalcs.UUCP (John Wright/Dr. Pat Lane)
Distribution: na
Organization: Math, Stats & CS, Dalhousie University, Halifax, NS, Canada
Lines: 52

last week, I posted the question: If you have a disk written on by a 360K
drive and re-format it with a 1.2M drive, are parts of the 360K track left
on the disk that could cause problems if the disk were subsequently read on
a 360K drive (Hmm.. that was much better phrased than my original question!)
I also asked if software "bulk erase" programs would be effective in 
preventing these problems and if so would they be equally effective if used
on a 1.2M drive.

I got got two contradicting answers.  One fellow posted, saying my fears were
founded, and that only a magnetic bulk eraser (or just a magnet) would re-
cycle a 360K disk for 1.2M use.  Another fellow mailed and said that floppy
drives use a "tunnel erase" and that on formatting (and maybe all writes) on
a 1.2M drive, any 360K track stuff is erased.  If I understood him correctly,
the only rason you get the 360K/1.2M problem is drive mis-alignment.

Well, them's the breaks, eh...

I was ruminating on the question and wondered if the 1.2M drives write every
second track in 360K mode, and if they start track 0 at the same diameter on
the disk then the situation would not be, as it is usually pictured:

 /////////////////////////                     /////////////////////////
 // residual 360K track //                     /////////////////////////
 /////////////////////////                     // residual 360K track //
 \\\\\\\\\\\\\\\\\\\\\\\\\                     /////////////////////////
 \\\\\\\ 1.2M track \\\\\\       but:          /////////////////////////
 \\\\\\\\\\\\\\\\\\\\\\\\\                     \\\\\\\\\\\\\\\\\\\\\\\\\\
 /////////////////////////                     \\\\\\\\ 1.2M track \\\\\\
 // residual 360K track //                     \\\\\\\\\\\\\\\\\\\\\\\\\\
 /////////////////////////                     \\\\\\\\\\\\\\\\\\\\\\\\\\

 (these drawings not to scale!)


 If the latter is the case, it would seem it me, that it would be possible
 for the 1.2M drive to write pairs of identical concentric tracks (instead
 of skipping every second track) and thus produce a 360K disk that is
 identical to one written on a 360K drive.

 I suppose there's a real good techno-reason why this won't work but if
 it did it would solve this whole 360K/1.2M mess, wouldn't it?

 Any comments?




-- 
John Wright      /////////////////     Phone:  902-424-3805  or  902-424-6527
Post: c/o Dr Pat Lane, Biology Dept, Dalhousie U, Halifax N.S., CANADA B3H-4H8 
Cdn/Bitnet: lane@cs.dal.cdn    Arpa: lane%dalcs.uucp@uunet.uu.net
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