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From: phil@brahms.amd.com (Phil Ngai)
Newsgroups: comp.windows.ms
Subject: Re: Drive>1024 tracks
Message-ID: <1991Mar26.173116.24802@amd.com>
Date: 26 Mar 91 17:31:16 GMT
References: <1991Mar25.104137.20709@agate.berkeley.edu> <17772@sdcc6.ucsd.edu>
Sender: usenet@amd.com (NNTP Posting)
Organization: Advanced Micro Devices, Inc.
Lines: 16

One thing you will want to know is that INT13 is the standard BIOS way
of accessing the disk. Unfortunately, IBM in their infinite foresight
and wisdom only allocated 10 bits for the track number.  Where you get
screwed is if the track number goes over 1024 and it wraps around to 0.

It is often physically possible. Many WD controllers, for example,
have 11-bit track registers. But you have to go directly to the
hardware.  Any use of the standard IBM INT13 could eventually result in
wrap around and trashing of your first few tracks.

Some programs like DM (presumably) install their own INT13. This is
ok until you have some application that bypasses the new INT13 but
only has 10 bits for track number. Then wrap around will occur again.

--
Sun PC-NFS: for the engineer who really want a Sun and got a PC.