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To: "John W. DeBoskey" <jwd@unx.sas.com>
cc: freebsd-current@freebsd.org
Subject: Re: fxp0 causes machine lockup 
In-reply-to: Your message of "Thu, 20 Nov 1997 23:07:08 EST."
             <199711210407.AA10760@iluvatar.unx.sas.com> 
From: David Greenman <dg@root.com>
Reply-To: dg@root.com
Date: Sat, 22 Nov 1997 12:13:07 -0800
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>   With respect to the following problem, the solution came from
>an unexpected location.
>
>   I asked our hardware support folks for a 2nd motherboard to see
>if the problem was specific to the hardware. Before getting the
>new MB, they suggested I upgrade the bios on my machine... I said
>sure, thinking FreeBSD doesn't use the bios, what could happen?
>
>   Dell OptiPlex PPro 200 with bios rev A00(Phoenix) flashed to A08.
>
>   The problem went away.
>
>   Could someone give me a short explanation of how the bios update
>could fix my apparent dma problem? Does the bios assign dma channels
>or something associated?

   The BIOS programs the motherboard chipset; it configures among other
things the various settings that control PCI DMA behavior. If the MB chipset
is misconfigured, then bad things can happen.

>   Anyways, I have now tested rev 0, 2, & 4 fxp NICs with complete
>success.

   Thanks for the note. BTW, does you machine have the 82557+82555
combination or does it have an 82558 chip?

-DG

David Greenman
Core-team/Principal Architect, The FreeBSD Project