5.4 fails to find boot drive, then panics.

[Mike Meyer]

I'm trying to install 5.4-RELEASE off of CDROM on an ASUS P5S800 motherboard
with a SATA drive in it. The SATA drive shows up as ad4 during the install
process, and the install goes just fine.

But the resulting system fails to boot. It goes through the boot sequence,
draws the cute 5.x booto menu, then issues the messages:

Can't work out which disk we are booting from.
Guessed BIOS device 0xffffffff not found by probes, defaulting to disk0:

panic: free: guard1 fail @0x5195c from /usr/src/sys/boot/i386/loader/../../common/module.c:957
--> Press a key on the console to reboot <--

Booting with debug messages doesn't change this at all.

There don't appear to be any bug reports related to this problem. Checking
google turns up a lot of peole who had this problem, but the only solution
was a guy who had a bad disk. I checked the md5 sum on the downloaded image,
and the software that I used to burn the image (Disk Utility on Mac OS X)
claimed to verify the burned disk - which I believe means it did a checksum
on the image and the disk.

There is an AGA DVD drive in the system on the secondary master. I thought
that it was getting confused by the drive numbers, and checked the bios to see
if I could turn off the ATA controllers. There's apparently no way to do that.

I suspect the panic is due to a bug in code that is only exercised if the boot
"can't work out which disk we are booting from." So if I can solve that, the
system should boot ok, and I can file a bug report for the panic. I'm hoping
that I can tweak a boot config file to solve the boot problem, and that someone
here knows what needs to be tweaked.

Maybe a diffferent boot loader would solve the problem?

	Thanks,
	<mike