Hi Roger,
Not entirely sure what is causing your problems, but there are several
options in your BIOS that are worth investigating.
http://www.supermicro.com/manuals/motherboard/HT2000/MNL-H8DSP-8i.pdf
Plug & Play OS
(might be worth setting this to "No")
KBC Clock Source
(try 8MHz)
S-ATA Mode
(IDE/MMIO or RAID, see if OpenBSD's behaviour changes)
ACPI Version Features
(1.0/2.0 or 3.0)
Another issue may be the UDMA mode, change "wd" again via UKC and
specify the flags 0xdfc (UDMA5,PIO 4).
Just some suggestions, which you may have already tried.
-Bryan.
