Date: Mon, 29 Sep 2003 16:04:19 -0400 (EDT) From: John Baldwin <jhb@FreeBSD.org> To: Dan Strick <strick@covad.net> Cc: freebsd-hardware@freebsd.org Subject: RE: bad BIOS confuses boot0 Message-ID: <XFMail.20030929160419.jhb@FreeBSD.org> In-Reply-To: <200309270624.h8R6OBjS000841@ice.nodomain>
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On 27-Sep-2003 Dan Strick wrote: > The AWARD BIOS on my Gigabyte 8KNXP motherboard has been giving me > a hard time for several weeks. Tonight I got around to instrumenting > a copy of /usr/src/sys/boot/i386/boot0/boot0.s and verified my > suspicion. > > The AWARD BIOS loads the MBR from the first drive in the BIOS drive > list, drive code 0x80, but passes the value 0x81 to the bootstrap > program through the %dl register. > > This has a couple of consequences: > > 1) The boot0 program lists the partition on the first drive but > boots the selected partition from the second drive, and > > 2) The boot0 program may overwrite the MBR on the second drive > with a copy of the MBR from the first drive. > > My workaround was to do: > > boot0cfg -Bv -d 0x80 -o setdrv,noupdate ad0 > > The noupdate option is intended to prevent a major disaster if > this drive should ever be assigned a different number by the BIOS. > > I don't like this workaround. It is clumsy and restrictive. > The drive configuration on my PC is in a state of flux. > > Has anyone noticed such antisocial BIOS behavior in the past? > > Is there actually a standard for passing the BIOS drive number through > the %dl register? Do I have grounds for *demanding* that the motherboard > manufacturer get the BIOS fixed? I don't think there is an actual standard for BIOS booting off a hard disk. The defacto standard is to indeed pass in the BIOS device number in %dl, so you likely can complain to your BIOS vendor. It's amazing Windows boots off the thing. Windows may hardcode 0x80 though as a workaround. The boot0cfg -d option exists to workaround this type of bug, so you are using the best workaround available. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/
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