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Path: utzoo!linus!decvax!cwruecmp!elwell
From: elwell@cwruecmp.UUCP (Clayton Elwell)
Newsgroups: net.micro.pc
Subject: Re:Re: A new IBM-compat from Apple
Message-ID: <840@cwruecmp.UUCP>
Date: Thu, 1-Dec-83 02:37:27 EST
Article-I.D.: cwruecmp.840
Posted: Thu Dec  1 02:37:27 1983
Date-Received: Fri, 2-Dec-83 06:35:48 EST
References: <733@ihuxm.UUCP>
Organization: CWRU Computer Engr. Cleveland, Ohio
Lines: 19

It's not misinformation.
The uPD765 (or 8272, if you like intel) in the PC needs the index hole,
even for soft sectoring.

The Apple Disk ][ drive/controller system doesn't even have the little
LED for detecting the index hole.  The Apple disk controller is a
masterpiece of simplicity.  It manages to pack 143K on a single-density,
35 track disk (using FM encoding, for hardware buffs).  It uses a
special self-synchronizing bit pattern in the interrecord gaps to find
the start of a sector, so it doesn't need the index hole.  In true Apple
style, if you don't need it, why bother?

The only practical way to read both formats with the same drive is to
put an Apple controller and a 765 in parallel.  The QuadLink board does
precisely this.  The only problem is that the Apple controller likes to
control the stepper motor directly, so you have to emulate it.

Details and documentation available upon request.