Asus P4S8X-X Linux and Hyperthreading

[Roberto Migliorati]

Hi all,

Please forgive the cross posting for cross posting, but I have done
extensive research on this subject and I didn't find any answer. I have an
Asus P4S8X-X motherboard, based on the SiS 648 chipset and a Pentium IV
3.06GHz with Hyperthreading enabled on the BIOS. Now under Windows XP Pro
(SP1a) I can see two (virtual) processors happily chugging along, and the
machine itself is *very* fast. I got rid of XP Pro (!!) and installed Red
Hat 9.0, Mandrake 9.1, Gentoo 1.4 RC4, and now (at my happiest!!)
Slackware 9.0, *all* with the appropriate SMP kernels, or, in the case of
Slackware that I am using now, recompiled the kernel with SMP enabled. The
issue is that *no* Linux distribution, no matter what kernel version, has
been able to show me two CPUs. Basically cat /cpu/procinfo still shows me
*one* Pentium IV at 3066MHz, and yes, it does tell me that HT is enabled
and supported. Having a look at my dmesg doesn't help either, no clues as
to why only one CPU is shown up and running, and no obvious errors of any
sort. Now, is this normal? Should I see one CPU and not two?? Maybe the
kernel knows I have two virtual cores available and distributes the
processes accordingly? I suppose that having an SMP enabled kernel would
mean that all the appropriate task schedulers and so forth should be
there. But I am not sure. If anybody has any ideas or can shed any light
on this, please post an answer, or even email me directly with some
clues!!
Thank you for being so patient and for listening!

Roberto.

 

[steveo]

Linux is a bit more intelligent than windows in a few areas, one of
which is processors.
Linux can make use of threads on ONE standard cpu to achieve the effect
of multiple CPU's.

As I understand it, SMP is for motherboards using >=2 physical
processors, which you are not. You have one processor which Linux will
allocate multiple threads where applicable.

Im not sure about this bit, but your P4 uses hyperthreading at a
hardware level not at a software level.

Basically you dont need SMP enabled in the kernel, Linux naitively uses
threading where as Windows XP doesn't.

Nice PC by the way