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From: oplinger@minerva.crd.ge.com (B. S. Oplinger)
Newsgroups: comp.sys.mac
Subject: Re: SE question
Message-ID: <3258@crdgw1.crd.ge.com>
Date: 16 Oct 89 20:13:05 GMT
References: <50037@<1989Oct2> <8400174@m.cs.uiuc.edu> <1989Oct12.231203.15676@NCoast.ORG>
Sender: news@crdgw1.crd.ge.com
Reply-To: oplinger@crd.ge.com (B. S. Oplinger)
Organization: General Electric Corp. R&D, Schenectady, NY
Lines: 26

In article <1989Oct12.231203.15676@NCoast.ORG> allbery@ncoast.ORG (Brandon S. Allbery) writes:
>As quoted from <8400174@m.cs.uiuc.edu> by gillies@m.cs.uiuc.edu:
>+---------------
>| How much difference is there between a superdrive and an IBM drive?
>| It's sad when a 1.44 3.5" IBM drive is $89 from CompuAdd, and
>| $350-$600 from Apple Computer, Inc.
>+---------------
>
>IBM-compatible drives use fixed speeds; Mac drives use variable speeds.
>The latter co$t$ more than the former, and supporting *both* co$t$ even more.
>(Why do Macs use variable speed drives?  Because 400K floppies are that much
>nicer than 360K floppies (SS/DD), and 800K better than 720K (DS/DD).  (Do
>SuperDrives provide a 1600K mode?)

Well, I'm definately sure that it is not density, as any Amiga or
Atari ST owner can tell you (they both use MFM 400/800K
floppies). I heard it was that the original design people at
Apple didn't understand the concept of fixed angular velocity and
chose a design which produced (somewhat) fixed linear speed. That
is, for each speed band the edges are within +/- n of the center
band speed ( which is the same for all center tracks ). Anyone
from Apple care to comment?

brian
oplinger@crd.ge.com
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