FC4 Kernel 2.6.14-1.1656_FC4smp shows wrong clock rate on Opteron 875

[Joachim Backes [RHRK]]

James Wilkinson wrote:

>Joachim Backes [RHRK] wrote:
>  
>
>>I'm running a Sun Fire V40Z server with 4xAMD Opteron 875 dual core 
>>(2.2Ghz). But looking for /proc/cpuinfo
>>shows for example for each (of eight) processors:
>>    
>>
><snip>
>  
>
>>I'm wondering about the clock 997 Mhz, because each processor should run 
>>with 2.2 Ghz.
>>Is this a display problem only, or does each processor core really run 
>>with 0.9 Ghz rate?
>>    
>>
>
>This is almost certainly due to cpuspeed. AMD64 processors come with
>what AMD call "Cool'n'Quiet", and Fedora knows how to use this. On a
>single-processor system, the processor will be slowed down to ~ 1 GHz
>(or 800 MHz on older processors) when there isn't much work for
>the processor to do. The voltage will be lowered, too, which saves quite
>a bit of power. That means there's heat being given off, which means the
>fans can go slower or stop, which means even less power.
>
>When system load picks up, the processor is returned to its "normal"
>operating speed.
>
>I don't have experience with multi-CPU Opteron machines under Linux, but
>I strongly suspect the same thing applies.
>
>Hope this helps,
>  
>

Hi, full hit. After stopping cpuspeed, each of the 8 CPUs is shown as 
running with 2.2 Ghz.
Thanks.

>James.
>
>  
>


-- 
Joachim Backes <joachim.backes at rhrk.uni-kl.de>
Registered Linux user #407492
University of Kaiserslautern,Computer Center [RHRK],
Systems and Operations, High Performance Computing,
D-67653 Kaiserslautern, PO Box 3049, Germany
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