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From: Terry Lambert <terry@lambert.org>
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: FreeBSD support [was Re: God Damn partition crap!]
Date: 10 Apr 1996 08:09:33 GMT
Organization: Artisoft, Inc.
Lines: 41
Message-ID: <4kfqbt$k2v@coyote.Artisoft.COM>
References: <4hqav8$kmo@nntp.interaccess.com> <4jlm89$7bm@calypso.bns.com.au> <4jptra$4h4@calypso.bns.com.au> <4jvbtg$mih@park.uvsc.edu> <4k5mdu$9ma@news1.halcyon.com>
NNTP-Posting-Host: hecate.artisoft.com
tzs@coho.halcyon.com (Tim Smith) wrote:
] Terry Lambert <terry@lambert.org> wrote:
] >Consider: I have two adaptec controllers. I load the software
] >INT 13 redirector for the second controller in my config.sys.
] >
] >How can Linux/BSD know the right geometry without loading the
] >same driver and making VM86() calls through that driver?
]
] Read sector 0, examine the partition map, and see which geometry is
] consistent with what you found there.
At worst, your protected mode OS will be the only OS on the
drive; it will have to guess what geometry will be available
to the boot blocks when they are loaded by the MBR and make
INT 13 calls using C/H/S, which is relative to the geometry,
to load the protected mode code.
At best, you will be left with an LCF problem because of
cylinder alingment, leaving you with one of several potential
geometries from the single DOS partition on the drive.
NB: LCF == Least Common Factor; iut's how you guess the BIOS
geometry that was used from on partition worth of hints (ie:
*one* C/H/S start value and *one* C/H/S end value which you
thing are cylinder aligned anyway, and the hope that the DOS
partition immediately follows the partition table as closely
as possible).
Note that OS/2 doesn't require an even sector boundry as long
as you have an even head boundry, so if your other OS is OS/2,
I guess your are just totally screwed.
Unless you really *fix* the problem instead of dancing around
a soloution using kludges to avoid the work.
Terry Lambert
terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.