# Open Hyper-Threading?

## inchlin

http://www.dell.com/us/en/esg/topics/power_ps3q02-morse.htm

So does gentoo support Hyper Threading?

I see the asus web page

845e,850e update the bios can support hyper threading

Does it means,

One p4 2.5a cpu can open hyper threading in bios

And enable in linux kernel?

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## inchlin

http://www.aslab.com/products/rackmount/lancelotc1850_tech.html

it seems state the procedure!

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## anatolli

the current generation of p4's don't support hyperthreading.  The P4 Xeons do, and intel is talking about releasing hyperthreading into the desktop market with the 3.06Ghz procs.  As of right now, if you don't have a Xeon, you don't have hyperthreading.

anatolli

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## keifir

so kernel would need no adjustment(extra programming) then to support the new HT intel chips?

One would be able to use HT by specifying that there multiple cpus available, is this right?

thx, keifir

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## dgtlchlk

The new 3.06ghz P4's do indeed support hyper-threading, but its more of a bios thing than software.

 *Quote:*   

>  so kernel would need no adjustment(extra programming) then to support the new HT intel chips? 

 

Correct, the kernel wouldn't need know anything about it, because it happens all internally to the cpu and bios

 *Quote:*   

>  One would be able to use HT by specifying that there multiple cpus available, is this right?

 

No, you wouldnt even need to specify that there were/was more than one cpu. Its all transparent to the system software.

At least i have yet to read a review online where any software had to be updated, but i could be wrong  :Smile: 

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## Tuna

hm.. no need for SMP kernel?

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## Forge

SMP kernel, yes, as the system acts like there are two CPUs past the BIOS level.

You also get SMP race problems and the like, and performance doesn't always increase... Sometimes it decreases, and a single HT CPU does NOT scale like two real CPUs do.

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## pilla

Note that SMP kernels add some overhead to control the race conditions. 

I don't think I'd pay more for a Hyperthreading processor while Linux does not have specific support for it (I think that it needs changes only in the scheduller, but who I am to say that  :Cool: ).

 *Forge wrote:*   

> SMP kernel, yes, as the system acts like there are two CPUs past the BIOS level.
> 
> You also get SMP race problems and the like, and performance doesn't always increase... Sometimes it decreases, and a single HT CPU does NOT scale like two real CPUs do.

 

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