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From: dclemans@mntgfx.MENTOR.COM (Dave Clemans)
Newsgroups: comp.sys.atari.st
Subject: Re: ST and IBM-PC using the same 3.5" disks: problem
Message-ID: <739@dclemans.mntgfx.MENTOR.COM>
Date: Thu, 18-Jun-87 12:46:50 EDT
Article-I.D.: dclemans.739
Posted: Thu Jun 18 12:46:50 1987
Date-Received: Mon, 22-Jun-87 01:14:42 EDT
References: <1415@batcomputer.tn.cornell.edu>
Organization: Mentor Graphics, Beaverton OR
Lines: 27
Summary: info on formatting


About problems interchanging 3.5" disks between ST's and PC's:

There are two potential problem areas:

1. The ST uses a Western Digital floppy controller chip.  PC's typically use a
   different one (NEC or it's Intel equivalent?).  Apparently under at least
   some circumstances the Western Digital 1772 can produce a low level format
   that the PC controller has trouble reading.

2. MS-DOS/PC-DOS initially put disk type information in the first entries in the
   disk FAT table.  Later revs have moved that information to sector 0; but for
   compatibility reasons disk type info is normally in both sector 0 and in the
   first FAT entries.

   GEMDOS on the ST only puts the disk type info in sector 0.  Therefore is a floppy
   driver on the PC expects to get the disk type info from the first FAT entries,
   it will get confused.

About sub-directory problems: while I haven't tried this from a "strict" PC/clone,
I have from an Amiga Transformer running PC-DOS 2.10 and 3.2.  The ST had no
problems reading those sub-directories.  A possible cause is that GEMDOS expects
to see "end-of-directory" at either the end of the sectors allocated to the directory,
or with an entry that starts with a zero byte.  If that wasn't the case you
definitely could get a crash.

dgc