Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!newstop!texsun!digi!kgallagh
From: kgallagh@digi.lonestar.org (Kevin Gallagher)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Can I Low Level Format my MFM drive with 17 < SECTORS < 26 ?
Message-ID: <1991Mar16.022315.28142@digi.lonestar.org>
Date: 16 Mar 91 02:23:15 GMT
References: <5832@trantor.harris-atd.com>
Organization: DSC Communications Corp, Plano, TX
Lines: 24

In article <5832@trantor.harris-atd.com> sonny@trantor.harris-atd.com (Bob Davis) writes:
>
>	I know that MFM normally uses 17 Sectors/Track and RLL uses 
>26 Sectors/Track. But is there a fundamental reason I cannot low
>level format my MFM drive to 20 Sectors/Track, say, in an attempt
>to increase drive capacity? Does the MFM controller FORCE the
>use of 17 S/T and the RLL controller 26 S/T or might they do whatever
>they are told by the Low Level Formatter program?

Without going into the technical details, the answer to your first question is
yes.  Given the fixed RPM of your drive, the MFM encoding technique, and the
speed at which the drive firmware writes to the disk, there is room for only
17 sectors/track.  If you try to write an 18th sector on a track, you risk
having part of the 18th sector overwrite part of the 1st sector.

If you slowed the RPM of the drive down, and you told the controller to write
more than 17 sectors per track, you would be able to write more sectors on a
single track; but the hardware might have trouble reading what your wrote,
especially on the innermost tracks.
-- 
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Kevin Gallagher        kgallagh@digi.lonestar.org OR ...!uunet!digi!kgallagh
DSC Communications Corporation   Addr: MS 152, 1000 Coit Rd, Plano, TX 75075
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