On Sat, May 09, 2009 at 01:56:09PM +0800, bill lam wrote: > > Personally I have noticed that locking my laptops scaling CPU to the > > lowest frequency does give quite a noticeable improvement to the battery > > life, around an extra hour on top of the usual 4~ hours and reduces the > > temperature enough to make the fan shut off . Just enabling on-demand > > scaling didn't help much as it would scale up to full frequency far to > > often. Even with the CPU locked in lo frequency mode it almost never lags. > > > > > > Thanks all for confirmation. Since I only have a desktop, no > notebook/netbook ;-( it is somehow difficult to verify the > improvement. I now lock the cpu frequency to 1.1GHZ (half of the > original 2.1G). > > Less heat means less power consumption, I guess someone suggested, > (I'm not sure that's why I asked for advise), that it takes more time > to complete the job at lower frequency so that actual power > consumption will in some case increase.
It's more efficient to run at full speed and then let the CPU halt (you have to have a tickless system though) [1-4]. Decreasing power consumption of sychronous processors is a really hard problem [5-7]. But anyhow I'm not a physicist or electrical engineer. Regards, Matthias-Christian [1] http://www.codon.org.uk/~mjg59/power/good_practices.html [2] https://www.redhat.com/docs/wp/performancetuning/Power_Management_Guide.pdf [3] http://www.ncsu.edu/wcae/ISCA2007/p52-suarez.pdf [4] http://lists.us.dell.com/pipermail/linux-poweredge/2007-December/033900.html [5] http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=3276&p=6 [6] http://patmos2001.eivd.ch/program/Repro%5CArt_10_1.pdf [7] http://async.org.uk/ukasyncforum14/forum14-papers/forum14-moore.pdf [8] http://www.fulcrummicro.com/press_archives/edn_03-0501.pdf
