> On Fri, May 8, 2009 at 9:08 AM, bill lam <cbill....@gmail.com> wrote: >> BIOS support choosing a smaller multipliers to reduce cpu frequency. >> linux also supports frequency scaling such powernowd. Some google >> page said cpu throttling can not reduce power consumption. My >> experience is that it seems to lower temperature. If it can also >> reduce power consumption, I'm willing to save money by running cpu at >> half of its current frequency. Any idea. > > My understanding is that power usage scales nonlinearly with CPU > frequency, and in particular having twice the frequency doesn't > require quite as much as double the power. So IF your OS can put your > PC into proper "sleep" states whent here's nothing to do (and that's > the big IF), the PC will use less energy in total by running at full > speed when you have work to do and then going into a sleep state > rather than taking twice as long to do the work at half the frequency. > So I'd expect you'd probably get more "energy usage reduction" from > getting rid of any services/device drivers/etc that stop the PC going > to sleep than from manually reducing the frequency. (If you're using > Linux, PowerTOP ( > > www.lesswatts.org/projects/powertop/ > > ) is an attempt to provide a way to at least see what's causing > wake-ups, even if it doesn't necessarily show how to solve them.) >> --
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.
