My Nephew, who is a bit of a computer whiz, recently gave me an 'old' 2.6GHz Prescott CPU to replace the Celeron in my desktop PC. This I have done and it is certainly faster.
However, I use gkrellm to monitor resource usage and whereas with the Celeron just a single window occurred for the CPU usage, now with the Prescott gkrellm shows two windows labelled CPU0 and CPU1 respectively. Googling Prescott I can find no mention of more than one core but it does have hyperthreading.
So my question is, how many (effective) CPUs do I have and is gkrellm accurately reflecting them??
Cheers
ian
On Fri, 2009-01-16 at 16:44 +0000, Ian Thompson-Bell wrote:
What you have there is a Hyperthreading CPU, which essentially supports two threads on the same processor therefore it looks like two cpu's from a software perspective.
The actual reason behind this (not the marketing reason) is that the execution pipeline on the Prescott series of CPU's was rather long which increases the chance of a cache miss where with a single thread your execution unit would be sitting idle..with two it has something to do.
Benefits vary and of course depend on an SMP aware kernel, there are also distinct kernel modifications that make up the difference between really having two processors and just being able to time slice between two simultaneous threads at a hardware level. But I will let you and google find them :)
Wayne Stallwood wrote:
On Fri, 2009-01-16 at 16:44 +0000, Ian Thompson-Bell wrote:
What you have there is a Hyperthreading CPU, which essentially supports two threads on the same processor therefore it looks like two cpu's from a software perspective.
Aha, I thought it might be something like that.
The actual reason behind this (not the marketing reason) is that the execution pipeline on the Prescott series of CPU's was rather long which increases the chance of a cache miss where with a single thread your execution unit would be sitting idle..with two it has something to do.
Benefits vary and of course depend on an SMP aware kernel, there are also distinct kernel modifications that make up the difference between really having two processors and just being able to time slice between two simultaneous threads at a hardware level. But I will let you and google find them :)
uname -a returns:
Linux ian-desktop 2.6.24-23-generic #1 SMP Thu Nov 27 18:44:42 UTC 2008 i686 GNU/Linux
so that looks SMP enabled - it is just the latest Ubuntu Gutsy kernel.
Guess I have some more Googling to do ;-)
Cheers
ian
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Ian Thompson-Bell -
Wayne Stallwood