I have an old Dell Precision 620 workstation with dual PIII 933's and 
512 Mb memory. It also uses AIC-7899P U160/m SCSI controllers with one 
U160 drive (boot drive) and one slower 18 Gb. I have been running many 
different variants of the kernel on this system for quite some time with 
much success. However, no amount of gnashing of teeth or pulling of hair 
have been able to get this system to boot ANY 2.6.12-rc1 (including 
2.6.12-rc1 vanilla, 2.6.12-rc1-mm3 and various RT patches) variant when 
the SCSI drivers are selected as modules (which is the way that I have 
always done it). Last night I built all of the necessary drivers into 
the kernel and the system boots fine.

I don't have an oops or anything that really helps diagnose this. The 
symptoms are: when booting init tries to load the modules from the 
initrd and usually loading of sd_mod produces several unresolved symbols 
  and it goes down hill from there. The symbols that it is bitching 
about scsi_request_normalize_sense, __scsi_mode_sense, 
scsi_logging_level, etc.) are in fact in scsi_mod (according to nm) 
which should have been and appears to have been loaded prior to trying 
to load sd_mod. I am attaching my config and output from lspci. If there 
is anything else that I have left out that I could provide, let me know.

I do have these kernels running without incident on my IDE based 
workstation at the office.

-- 
    kr