Ned Slider wrote on Sun, 03 Aug 2008 15:09:39 +0100: > http://www.centos.org/modules/newbb/viewtopic.php?topic_id=15484&forum=37 Thanks for the URL, see below! > > Bottom line - the power saving between having frequency scaling enabled > or not was surprisingly small (only 2-3W). It would appear that these > processors are already fairly efficient at idle and scaling down the > frequency adds little to the overall savings that may be obtained. I disagree about the reason. I think they are actually not so efficient. At least not if I compare to a low-voltage CPU. 105 W is a lot, latest AMD quad core low-voltage are at 50W. Did you check core temperature in the two scaling states? It makes a huge difference for me on the AMD (which is allowed to drop from 2500 to 1000). It drops from an already low value (30 and 22 Celsius) by more than 10 degrees. The second core always shows the lowest temperature (puzzle?) and it goes down to 6-8 (!) Celsius in idle state with 1000.) I think this will also result on some more substantial savings in Watt consumption. Even, if not, a substantially lower temperature like this is good for a long life of all parts, anyway. I read that thread and am puzzled by acpi-cpufreq being loaded on your machine. If I modprobe it I get an error "device busy". Which makes sense to me as cpufreq_ondemand (which loaded automatically) should have already taken over. I see that behavior on all machines, no matter if Intel or AMD. >From my research yesterday it also looks like use of acpi-cpufreq is somewhat "older" and should not be necessary at all for newer CPUs. So, it should be cpufreq_ondemand alone that does the scaling on your machine. Can you confirm that? I also wonder if your machine actually scales up. You listed the output in low/idle state. As I wrote I get the same, just at another level (they probably think Xeon's will be active all the time, anyway, so they allow them to drop not so much). Did you check that the frequency actually goes up to 2400 under load? Kai -- Kai Schätzl, Berlin, Germany Get your web at Conactive Internet Services: http://www.conactive.com