Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!gatech!purdue!bu-cs!dartvax!eleazar.dartmouth.edu!genemans
From: genemans@eleazar.dartmouth.edu (Jan Genemans)
Newsgroups: comp.sys.ibm.pc
Subject: Re: make your own HD 3 1/2 in floppies
Message-ID: <14333@dartvax.Dartmouth.EDU>
Date: 11 Jul 89 12:56:47 GMT
References: <26260@amdcad.AMD.COM> <26262@amdcad.AMD.COM>
Sender: news@dartvax.Dartmouth.EDU
Reply-To: genemans@mac.dartmouth.edu (Jan Genemans)
Organization: U.S.M.M.A., Kings Point, NY
Lines: 31

In article <26262@amdcad.AMD.COM> ching@pepsi.AMD.COM (Mike Ching) writes:
>In article <26260@amdcad.AMD.COM> phil@diablo.amd.com writes:
>>
>>I just ran an experiment with double sided 3 1/2 in floppies.  On one,
>>I melted a hole in the corner with a soldering iron.  On another, I
>>cut the entire corner off and then resealed it with a soldering iron. 
>>
>>I then tried formatting as 1.44 Mb floppies -- it worked!
>>
>Anyone know how the 1.44Mb floppies achieve the density? More tracks?
>More sectors/track? *Should* this work? You can't use 360K 5 1/4"
>floppies at 1.2M because the coercivity of the coating is different but
>you can make them 720K by doubling the number of tracks.

If anyone is going to try this, they should be forwarned.  I have used ~500
disks in the 720k format with only 2 failures.  However, when I converted the
disks into 1.44M with soldering a hole in them roughly one out of five disks
had a failure, thus a ~5000% increase in disk failures.  If you insist on
modifying the disks to a higher density than rated make sure that you backup
*everything* or you might loose valuable data.  As for the 5.25" DS/DD format-
ted as 1.2M DS/HD I had a failure rate of 50% or 5 out of 10 disk attempts.
Other people might have different results, however, I strongly advise that
this should not be done because of the headache of loosing data, even if it
backed up.

I suspect that the "coercivity of the coating" is different for the 1.44M as
well as the 1.2M in comparison to the lower density disks.
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