Re: Problem determining number of CPUs

From: Kelsey Hudson (
Date: Wed Aug 21 2002 - 16:06:28 EST

On Wed, 21 Aug 2002, Nagy Tibor wrote:

> Hi,
> Linux kernel versions 2.4.18, 2.4.19, 2.4.20pre4 do not determine
> correctly the number of CPUs on our system. We see 8 CPUs instead of 4,
> however the system works.
> Our machine: Dell PowerEdge 6600, 4 Xeon 1400 Mhz, 4GB RAM

Perfectly normal on that machine; newer Xeon CPUs have a feature called
hyperthreading, which makes each physical CPU show up as two. If you have
many threads running, or a bunch of processes, you should see a
performance increase. but keep in mind that for each physical CPU you
still only have one CPU core, so you can't expect to run 8 tasks at full
speed. Hyperthreading uses idle cycles on one task to perform active
cycles on another task, in its most basic sense. I'm not going to delve
into great detail here as it's off-scope for this list, but if you read
the datasheets and product specification for the Intel Xeon processor
(available at Intel's developer site) you can learn more about this nifty
feature of these processors.

Hope this cleared up some questions you may have had.

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This archive was generated by hypermail 2b29 : Fri Aug 23 2002 - 22:00:23 EST