Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!oliveb!tymix!tardis!jms
From: jms@tardis.Tymnet.COM (Joe Smith)
Newsgroups: comp.sys.amiga
Subject: Re: disk size ...
Summary: Amiga not same as Mac
Message-ID: <269@tardis.Tymnet.COM>
Date: 22 Jun 89 23:57:25 GMT
References: <4167@merlin.usc.edu>
Reply-To: jms@tardis.Tymnet.COM (Joe Smith)
Organization: McDonnell Douglas Field Service Co, San Jose CA
Lines: 25

In article <4167@merlin.usc.edu> wdao@castor.usc.edu (Walter Dao) writes:
>Couldn't one write more data on track 0 (outer most) than on track 80
> (innermost) ? .

As long as the drive uses a constant speed (RPM) and the disk controller uses
a constant frequency (bits per second), the outer tracks will hold the same
number of bytes as the inner tracks.  That's the easiest way to design the
hardware, even though it means that the bits are farther apart on the outer
tracks and squeezed too close on the inner tracks.

By increasing the data clock or decreasing the motor speed, one can put more
bytes on the outer tracks.  Apple does the latter on the Macintosh drives,
using 8, 9, 10, 11, and 12 sectors per track, depending on which track it
is reading.

Which leads to a commonly asked question: Why can't the Amiga read Mac
floppies?  Answer: Because it wasn't designed to.  Hacking with the existing
hardware does not work; the only reliable way to do it is to use a different
drive.  Such as plugging an Apple compatible disk into the A-MAX box.

-- 
Joe Smith (408)922-6220 | SMTP: JMS@F74.TYMNET.COM or jms@tymix.tymnet.com
McDonnell Douglas FSCO  | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms
PO Box 49019, MS-D21    | PDP-10 support: My car's license plate is "POPJ P,"
San Jose, CA 95161-9019 | narrator.device: "I didn't say that, my Amiga did!"