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dazdaz 03-30-2004 06:49 AM

Detecting hyper threading
How do I detect if hyper threading is enabled in the BIOS from within Linux ?

Many thanks

jkobrien 03-30-2004 07:35 AM

The "top" command will show you how many processors are running. If it's twice the actual number of processors, then hyper-threading is enabled and working.


dazdaz 03-30-2004 08:15 AM

This does'nt help. Say you don't know how many processors the box has without physically checking.

That was the point of the question, I don't want to physically check.

Does anyone know ?

Thanks anyway for the reply.

SciYro 03-30-2004 08:23 AM

look somewhere in the /proc FS i think?, i know i remember reading something that said "linux can detect hyper threading while windows only thinks theres 2 processors" (this was before windows become hyper threading compatible), but i never tried to see how to detect it

jkobrien 03-30-2004 08:29 AM

You could look at the output from dmesg. My system has the following close to the start of the dmeg output...

cpu_sibling_map[0] = 1
cpu_sibling_map[1] = 0
cpu_sibling_map[2] = 3
cpu_sibling_map[3] = 2

I, perhaps wrongly, interpret this as output from the system as it enables hyper-threading.

Although this still wouldn't help you if the BIOS enabled hyperthreading but the kernel didn't.


waster 03-30-2004 03:46 PM

what about enabling hyperthreading if it's disabled in the BIOS, or am I pushing my luck? My laptop BIOS is so basic there is no mention of it, but I presume every P4 2800 has this capability. Does anyone know of any software or HOWTO which discusses this?

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