Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!ames!pasteur!ucbvax!hplabs!hp-sdd!megatek!zeta!hollen
From: hollen@zeta.megatek.uucp (Dion Hollenbeck)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Question about diskette densities
Message-ID: <586@megatek.UUCP>
Date: 20 Jun 89 14:46:28 GMT
References: <1559@cbnewsh.ATT.COM>
Sender: news@megatek.UUCP
Lines: 28

From article <2210@bingvaxu.cc.binghamton.edu>, by vu0112@bingvaxu.cc.binghamton.edu (Cliff Joslyn):
> 
> I'm beginning to doubt common sense about diskette densities.  Both
> single and double sided diskettes can be formatted as if they were
> double.  I'm told it's simply a difference in quality control.  On my
> new 1.2 meg 5.25" drive I can format DS/DD disks at 1.2 meg?  What am I
> risking by not buying HD disks?  etc.


You didn't ask this, but it may help someone.  DSDD disks can be 
formatted for up to 800k.  This is an unusual configuration because
it uses 10 sectors per track which the UCSD p-System does reliably,
but I never figured out why MS-DOS only used a max of 9 per track.
The format using 9 sectors per track is 80 tracks of 8 sectors for
a total of 720k.  You merely need to tell DOS via DRIVPARM or by
using DRIVER.SYS that you have a 720k 3 1/2" drive and it will not
know that you really have a 720k 5 1/4".  BTW, you must have the
correct disk drive (like a Shugart 465).  A standard 360k drive will
NOT make or read 720k disks and a 720k driver will not make or read
360k disks.  FASTBACK PLUS can be configured to recognize these
drives as 720k drives and works perfectly.  In fact, this is the
use I have put them to.

	Dion Hollenbeck             (619) 455-5590 x2814
	Megatek Corporation, 9645 Scranton Road, San Diego, CA  92121

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