Asus P4S8X-X, HyperThreading and more...!

[Roberto Migliorati]

Hi all,
I have a few questions regarding my HW when it comes to Linux. I am using an
ASUS P4S8X-X motherboard based on the SiS 648 chipset with 1GB of RAM and a
Pentium IV at 3.06GHz with HT enabled on the BIOS (stock standard 1002). Now
under Windows XP Pro (SP1a) I can happily see my two virtual CPUs with their
respective CPU Usage History Charts. I have to say that the machine is
actually *very* fast, especially with apps like Photoshop 7.0.1.
The point is I would rather use Linux and The Gimp. I installed Red Hat 9.0,
Mandrake 9.1, Gentoo 1.4 RC4, tried FreeBSD 5.1 (which just freezes at
install!!) but I can't see 2 (virtual) CPUs under Linux. No matter what
kernel I used or compiled myself, I always get ONE CPU. Now, I am aware I
might be absolutely off track here, and one CPU is *all* I am supposed to be
seeing, but a few Google searches and documents on the Intel web site tell
me that indeed there should be *two* and not one.
Am I correct?? I tried enabling/disabling APIC to no avail.

Please help!

Thanks,

Roberto.

 

[athol]

No matter what
kernel I used or compiled myself, I always get ONE CPU. Now, I am aware I
might be absolutely off track here, and one CPU is *all* I am supposed to be
seeing, but a few Google searches and documents on the Intel web site tell
me that indeed there should be *two* and not one.
Am I correct?? I tried enabling/disabling APIC to no avail.

You need to enable SMP. Build an SMP kernel and the 2 processors
will be enabled during startup. You can check back with dmesg to
check that it worked...

 

[Roberto Migliorati]

I should have mentioned that before, but I already tried SMP kernels,
pre-packaged and compiled by myself, to no avail....any other idea?? Anybody
got the same system working (in SMP mode) under Linux??

Thanks,

Roberto.

 

[athol]

I should have mentioned that before, but I already tried SMP kernels,
pre-packaged and compiled by myself, to no avail....any other idea?? Anybody
got the same system working (in SMP mode) under Linux??

How recent a kernel are you using? I tried to get SMP working on
my new P4 using 2.4.21 and eventually discovered that the 2.4GHz
533MHz FSB processor doesn't have 2 virtual processors even though
it sets the HT flag! If your version of kernel pre-dates HT, it
won't know how to enable it!

In dmesg, I kept getting a message to the effect that
hyperthreading was disabled. When I downloaded about 30Meg of
data sheets, programming manuals etc from Intel, I eventually
discovered that there are P4 chips that set the HT flag, but when
you check for HT, they return the number of virtual processors
available in a group of bits in one of the other registers, and
the return value of 1 means no hyperthreading and a message in
dmesg of "hyperthreading disabled". If it is 2, HT is enabled
and it starts up the 2nd processor. There is an error message in
the kernel for numbers over 2, just in case.

Consequently, No, I haven't got HT working until I trade in my
P4 2.4 on one with HT in 6 or 12 months. :-(

 

[s]

You need to enable SMP. Build an SMP kernel and the 2 processors
will be enabled during startup. You can check back with dmesg to
check that it worked...

I had a compaq proliant ml370 with a single HT chip work under RH8.0. I
could see both virtual cpus in /proc/cpuinfo.

Did a little testing and couldn't seen any time improvements, but i never
really tried any heavy, parallel loads, it was mostly single task stuff.

At home i've got dual cpus, and the biggest impact seems to be that the
machine is always responsive, it never bogs down when busy, even with 'make
-j 30' i can still play solitaire, i've also the pre-empt patch happening.

 

[Roberto Migliorati]

How recent a kernel are you using? I tried to get SMP working on
my new P4 using 2.4.21 and eventually discovered that the 2.4GHz
533MHz FSB processor doesn't have 2 virtual processors even though
it sets the HT flag! If your version of kernel pre-dates HT, it
won't know how to enable it!

Sorry to reply so late but....first of all my P4 IS HT enabled (3066MHz,
it is the only HT P4 with a 533MHz bus) second I used Kernels from 2.4.21
up to 2.6.0-test1, still no avail. Some people also make some confusion
between Pentium 4 with HT core and Xeon with HT. Despite the fact that
they are *quite* similar, they are *not* the same.

Thanks for your help anyhow!

R.

 

[Roberto Migliorati]

I had a compaq proliant ml370 with a single HT chip work under RH8.0. I
could see both virtual cpus in /proc/cpuinfo.

Did a little testing and couldn't seen any time improvements, but i never
really tried any heavy, parallel loads, it was mostly single task stuff.

At home i've got dual cpus, and the biggest impact seems to be that the
machine is always responsive, it never bogs down when busy, even with 'make
-j 30' i can still play solitaire, i've also the pre-empt patch happening.

Does the ML370 come with a Pentium 4 or a Xeon processor(s)??

Thanks.