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From: briand@tekig4.UUCP (Brian Diehm)
Newsgroups: net.micro.mac
Subject: Re: 800k drive formats (A proposal)
Message-ID: <751@tekig4.UUCP>
Date: Thu, 19-Jun-86 13:57:28 EDT
Article-I.D.: tekig4.751
Posted: Thu Jun 19 13:57:28 1986
Date-Received: Sun, 22-Jun-86 03:12:47 EDT
References: <262@sivax.UUCP>
Reply-To: briand@tekig4.UUCP (Brian Diehm)
Distribution: net
Organization: Tektronix, Inc., Beaverton, OR.
Lines: 31

>Why not just allocat sectors 0-800 (approx) to the first side, the 801-1600
>to the second???   It would solve ALOT of current problems (some caused by
>user cheapness, but what the heck)
>
>1) A disk could be initted as 800k, then a copy-protected disk could be copied
>to it in bit copy mode.  A utility could be then written to tweak it back to
>800k and voila, a useable 800k disk with the 400k copy protection intact!!! 

Your suggestion, while maximizing compatibility between different formats,
costs in terms of performance.  It halves the amount of sequential data avail-
able to the drive without seeking - i.e., while the same amount of data is
under the heads, it is divided into two unrelated segments.  The way it is
cuts the number of seeks in half when reading long sequential files, provided
they are not fragmented.

IBM chose your suggested methodology for 5.25 drives; most disk designers were
appalled at the choice.  It was simply some questionable compatibility in
exchange for a heavy performance penalty - and performance was one of the things
that double-sided users were after.  In my opinion, I've paid money for the
extra capability of a different format, and I knew good and well that it WAS
a different format.  Pseudo-compatibility just raises more problems than if
you simply tell people "It's a different format, so forget it.  You can't use
a double sided disk in a single sided drive."  Trying to do that confuses
everybody, and messes up performance for those who have paid for it.

-Brian Diehm
Tektronix, Inc. (The above is only MY opinion, the opinions of other people at
                 this company may differ, and I don't think Tektronix has a
                 company stand on this one way or another but I could be
                 wrong.  Why I remember once in 1954 I thought I was wrong,
                 but. . .)