# Hyperthreading on my 2 XEON prestonia CPU's

## nicke

Hi all!

I am wondering... Once when I installed Gentoo, my prestonia CPU's were recognized and top showed CPU0, 1,  2, 3. Now after my reinstall, my CPU's are only recognized as ordinary ones.. CPU 0 and 1. What do I have to do to enable this feature in the kernel? Any input on this matter will be much appreciated.

Many fanks. =D

nicke

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## nicke

So, i've come to the conclusion that i have to pass a kernel message in my boot-loader. What i do not yet know is the syntax! I would be greatful for any input!

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## delta407

You can pass parameters to the kernel at boot by editing your /boot/grub/menu.lst file. Just mount your /boot partition, open menu.lst, and look for the line that says "root=/dev/hda3" (or similar). You can add parameters on that line.

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## nicke

I know all this, but thanks for pointing that out anyway!

After the kernel command that has allready been given I add my command for enabling hyperthreading, which is: acpismp=force.

This command however seems to be ineffective.

Thus, my HT is still not enabled.

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## Forge

You may want to try a stock kernel. HT might be broken in the Gentoo-specific ones.

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## rSYN

I'm trying to do this also. I can't get anywhere. My kernel shows only 2 cpus.

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## delta407

 *Forge wrote:*   

> HT might be broken in the Gentoo-specific ones.

 

While that may be the case, most of the reports of working hyperthreading are with the 2.4.19 series, so try 'em anyway.

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## Sivar

You might reconsider using HT at all. It is of dubious value and actually slows down some server operations. Not sure about using it as a desktop system. Most people that use Gentoo use it as a desktop as it isn't really quite ready for a server. You might look at SuSE, Redhat (cringe), or Debian for that.

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