Pentium 4 HT?

Kenji Miyamoto · Posted: Sat Jun 24, 2006 7:49 pm Post subject: Pentium 4 HT?

I've recently acquired a Pentium 4 2.4 GHz, and was wondering if it has HyperThreading support. In lshw, one of the capabilities listed is 'ht'. Is this it?
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eroyf · Retired Dev Joined: 03 May 2004 Posts: 82

Yes it is. Just enable SMP and the HT thing which pops up when you enable SMP in the kernel

think4urs11 · Posted: Sat Jun 24, 2006 7:56 pm Post subject:

iirc ht support depends on FSB frequency.
I do have a P4-2.4 here too - it has the ht flag listed but is definately *not* ht-capable.
If yours has FSB400 then (most probably, as mine) no, if FSB533 then yes.
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eroyf · Retired Dev Joined: 03 May 2004 Posts: 82

asfaik started Intel with HT in their 2.4Ghz CPU's and above. My laptop didn't have ht and didn't have the "ht" flag in /proc/cpuinfo

Im not sure that FSB has anything to do with it? But not sure o_O

think4urs11 · Posted: Sat Jun 24, 2006 8:10 pm Post subject:

i stand corrected, it's not exactly dependand on the FSB but the core used.
Willamette: no HT
Northwood: partly (revision C and 3.066GHz) - thats mine with 2.4GHz, rev A
Prescott: mostly

reference (among others): http://en.wikipedia.org/wiki/Pentium_4
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Kenji Miyamoto · Posted: Sat Jun 24, 2006 8:18 pm Post subject:

I got this CPU from a friend, and it wasn't in its original box; where would I find information on the FSB after the multiplier? lshw says it's at 147 MHz.
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eroyf · Retired Dev Joined: 03 May 2004 Posts: 82

Try build a kernel with SMP and HT. Then you can see two CPU's in /proc/cpuinfo

Here is output from my workstation which has HT enabled.

Kenji Miyamoto · Posted: Sat Jun 24, 2006 8:34 pm Post subject:

Well, it looks as though there isn't HT support; I have it enabled in my kernel and nothing is different. Back to the non-SMP kernel.
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eroyf · Retired Dev Joined: 03 May 2004 Posts: 82

I need to enably my HT support in the BIOS. Did you have a look there?

Kenji Miyamoto · Posted: Sat Jun 24, 2006 8:49 pm Post subject:

Nothing of HT was in the BIOS configuration.
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rhill · Posted: Mon Jun 26, 2006 4:03 am Post subject:

ht will appear in /proc/cpuinfo for a lot of P4 and greater processors that don't actively support it. the architecture supports it, but for whatever reason (technical or financial :wink:

) Intel has disabled it in that model/stepping. I have three different P4's here, all of which have an ht flag in cpuinfo, but only one actually supports it.
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bollucks · l33t Joined: 27 Oct 2004 Posts: 606

The HT flag tells you that the cpu architecture supports hyperthreading. It does not tell you if there is a logical 2nd threading unit to have 2 cpus. The sibling count gives you that. In /proc/cpuinfo:
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid xtpr

has ht

but

siblings : 2

tells you that there are 2 logical cpus. If your cpuinfo reads 1 there you don't have hypethreading.

and

cpu cores : 1

tells you there is one physical cpu

Only more recent kernels give you the sibling count. Prior to that you had to query the cpu with other tools