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From: Terry Lambert <terry@lambert.org>
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: sd2/2 FreeBSD installation problem
Date: Sun, 29 Sep 1996 16:42:12 -0700
Organization: Me
Lines: 30
Message-ID: <324F0954.D29747F@lambert.org>
References: <51pdak$s1@ns1.win.net> <3244C4A3.ABD322C@freebsd.org> <52jo5g$8s@uriah.heep.sax.de>
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J Wunsch wrote:
] _However_, their ability to select another drive than ID 0 as a boot
] drive _should not_ be used. This is meant to be a silly-DOS method
] for booting off another drive than 0, but due to DOS' (and other
] system's) constraints, they do it AFAIK by reassigning BIOS ID 0x80 to
] the new boot device. This conflicts with FreeBSD's expectation, so
] you end up with a mismatch between BIOS and FreeBSD devices (BIOS
] drive 0x80 == ``C:'' != FreeBSD sd0).
You have the same problem with two controllers in any case.
FreeBSD probe order can not be guaranteed to be equal to
BIOS POST-initiated INT 13 chaining order.
The Only fix would be to use VM86() calls to identify the BIOS
device via MD5 checksum or other method, and compare the results
with a similar application of the method to a read from the
FreeBSD protected mode device.
This is, in fact, what the Windows 95 TSD portion of the VFAT.VXD
driver does in order to mape TSR and other pre-Windows 95 file
handles to protected mode driver file handles (disassembly is
left as an exercise for the student with a copy of WINICE or of
"Sourcer" from V Communications, Inc.).
Terry Lambert
terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.