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From: zlraa@iceman.jcu.oz (Ross Alford)
Newsgroups: comp.os.cpm
Subject: Re: Spell21
Summary: use DSDD disks
Message-ID: <859@iceman.jcu.oz>
Date: 24 Jul 90 11:21:31 GMT
References: <14141@wpi.wpi.edu>
Organization: JCUNQ, Townsville, Qld, Australia
Lines: 15

The question was:  what sort of disks to use in a DSQD drive for
820k.  The poster tried HD disks, and they didn't work.  Not
surprising:  HD disks have greater coercivity, meaning they are 
more resistant to magnetisation, and need stronger write flux.  This
allows more sectors/track without adjacent regions affecting one another
What you really want are DSQD disks, certified for quad density.  I
haven't seen these advertised for some time, but not to worry--I've thus
far used over 150 DSDD disks at 720k in a TEAC quad drive and have had
no failures, despite using a variety of no-name generic disks.  If you
are a worrier, run a verify program after formatting.  DSQD disks, when
they were available, were simply standard disks that had been tested
at quad density.

Ross Alford
zlraa@iceman.jcu.oz