Dell Optiplex GX280 hyperthread does not work

[Tibor Radvanyi <tibor.radvanyi@gmail.com>]

Hi,

I've installed Sarge on a Dell Optiplex GX280. I can boot it only with
acpi=off, any other acpi related kernel parameter results a hanging
boot process writing
   Real Time Clock Driver v1.12 
for the last time. 
I installed the 2.6.8 smp kernel package in order to have the benefits
of the hyperthread enabled processor, but I can see only one CPU
mentioned in /proc/cpuinfo or the output of top booting the smp kernel
(with acpi=off). acpi=ht, acpi=force does not boot.
Is there a relation between acpi=off and hyperthreading? How could I
use the virtually 2 processors on this computer? How should I config
my kernel if have to compile it?