Booting kernel-2.6.7-1.476.i586 on an Opteron system (IBM x325) with
acpi=off works fine. Booting without acpi=off causes the bootup to
hang at 'Calibrating delay loop...'.
Do new kernels behave?
The latest kernels (2.6.9-1.640 for example) do not boot on the x325
with acpi on
can you see if you can get something out of serial console with this ?
maybe try initcall_debug too.
does it boot with "noapic"?
does it boot with "acpi=noirq"?
no reply for over a year, assuming fixed.