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Date:      Sun, 23 Feb 2003 21:45:51 -0800
From:      Terry Lambert <tlambert2@mindspring.com>
To:        Hiten Pandya <hiten@unixdaemons.com>
Cc:        current@FreeBSD.ORG
Subject:   Re: machdep.guessed_bootdev sysctl on i386
Message-ID:  <3E59B18F.3D0D4CC3@mindspring.com>
References:  <20030224024210.GA50286@unixdaemons.com>

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Hiten Pandya wrote:
> Hello gang.  Nothing big, but important...
> 
> Can someone tell me if the machdep.guessed_bootdev sysctl is helpful at
> all?  I think it's a waste, and it's pretty limited and only available
> on the i386.
> 
> It currently guesses 'wd' instead of 'ad' for the dev. nodes, .e.g:
> 
>         hiten:~/> sysctl machdep.gussed_bootdev
>         machdep.guessed_bootdev: /dev/wd0s1a
> 
> SCSI drives are shown right (da) but ATA drives mess up, i.e. it is
> still thinking we have the 'wd' system.  It's either that we nuke this
> sysctl or apply the attached patch to sysctl, which has been reviewed
> and tested by people on IRC with positive results.

I've seen this used with FORTH code in order to automatically
identify the correct device, after a failure to load modules
from the wrong "guess".

The "guess" comes from the BIOS.  THere are some Dell systems
where the BIOS doesn't set up the BX register correctly; I don't
know if there are any systems besides Dell where this is an
issue.

-- Terry

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