The good news about the BIOS update is that my 3.99.8 install ISO appears to 
work correctly, something it didn't do before. So I have a fallback.

I'm trying to get the 3.99.24 ISO I got from Greg working. The INSTALL_ACPI 
kernel works, but none of the real kernels on the CD find all the disks (in 
particular, they don't find the root disk). I might be able to fix that by 
swapping things around, and may do that. I'm suspicious that the GENERIC_ACPI on 
the CD also has MULTIPROCESSOR...

What a mess. But maybe forward progress.