Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!shadooby!ginosko!usc!snorkelwacker!paperboy!husc6!m2c!wpi!dseah
From: dseah@wpi.wpi.edu (David I Seah)
Newsgroups: comp.sys.apple
Subject: Re: Reading 720k disks with the Apple 3.5 Drive
Message-ID: <4990@wpi.wpi.edu>
Date: 24 Oct 89 00:28:34 GMT
References: <8910200601.AA21133@trout.nosc.mil>
Reply-To: dseah@wpi.wpi.edu (David I Seah)
Organization: Worcester Polytechnic Institute, Worcester, MA. USA
Lines: 21

In article <8910200601.AA21133@trout.nosc.mil> jeffn@pro-europa.cts.com (Jeff Noxon) writes:
>[Ponderings regarding 720K disk reads via Smartport deleted]
>Also, someone mentioned something about Apple 3.5 drives speed control
>that didn't sound quite right.  I can't find that post now.  Anyway,
>the 3.5 operates at a variable recording speed depending on the track.
>The drive automatically adjusts this speed so it can fit the same amount
>of data on every track.

I'm pretty sure that the drive adjusts its speed so it can fit VARIABLE
amounts of data from track (or group of tracks) to track.  By varying the
drive speed, the track being read can be kept at a constant linear velocity
with respect to the read/write head.  With a fixed speed drive, angular
velocity is constant.  This doesn't take advantage of the physical track
length differences.  The outer tracks are longer (ala 2*pi*radius) than the
inner tracks, and hence can hold more data.  Since the data read/write is
clocked, ya got to vary the drive speed to use it all.

Another garbled followup from
-- 
Dave Seah | O M N I D Y N E  S Y S T E M S - M |   Internet: dseah@wpi.wpi.edu 
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