dual xeons and linux kernel - sees 4 processors instead of 2. Why?

Jacob Bunk Nielsen jbn at exiqon.com
Thu May 18 07:39:54 CDT 2006

"Paul" <ptuohy at digibug.com> writes:

> I have a Poweredge 1800 with dual Xeon processors. I just compiled the linux
> kernel. In the kernel config, I set the Maximum number of CPUs
> (NR_CPUS) to 2 because I have 2 processors. However, I notice that the boot
> message reports the following:

Don't you think it's because it uses hyperthreading? You can try to
disable hyperthreading from the BIOS.

> Is this because the Xeon processors are 64bit? Does the kernel see each
> processor as 2 CPUs. Is there something wrong? Can anyone explain this to
> me?

Some of the older 32 bit Xeons also have hyperthreading and show up as
two processors to the operating system.


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