p4 and hyper-threading

Dave Jones davej at redhat.com
Wed Jan 7 21:50:07 UTC 2004


On Wed, 2004-01-07 at 21:00, Castelhano, Dan wrote:

> I seem to be unable to make the hyper-threading functionality of my Pentium
> 4 3.2ghz processor work. I've searched google and redhat/fedora list
> archives and haven't found a similar post to this problem, so I have no idea
> what is wrong.
> 
> *This is an HP system, with the latest BIOS
> *Hyper-threading is enabled in bios
> *Added acpismp=force to my grub boot line (kernel /vmlinuz-2.4.20-28.7smp ro
> root=/dev/hda7 hdc=ide-scsi acpismp=force) - saw a blub somewhere on the net
> to add this to make it work, although it seems to do nothing in my case.
> *Applied every single errata update redhat has for 7.3 
> *Using redhat kernel: kernel-smp-2.4.20-28.7 (uname -a: Linux ---
> 2.4.20-28.7smp #1 SMP Thu Dec 18 11:18:31 EST 2003 i686 unknown)

HT support isn't in that kernel. You'll need the Fedora kernel.
(or mainline 2.4.21 or above)

> >From my readings and previous experience with the p3 hyperthreaded xeons,

There are no HT P3's. Hyperthreading is something exclusively for P4's.

> Side note: when I was setting up this system, the redhat installer installed
> the smp kernel so it must see something for it to have picked the smp
> kernel, otherwise it would have picked the base non-smp kernel...right? so
> why isn't it reporting anything about a 2nd logical proc?

The installer saw the BIOS tables describing the 2nd processor.

> Does anyone have any other ideas of what I can check/change to make
> hyper-threading work on this p4? Is anyone running fedora with this type of
> chip and seeing the 2 logical processors (unlike me)?

Upgrade is really the easiest option.

	Dave





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