On Monday 16 July 2007, T?r?k Edvin wrote: > On 7/16/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > First, I noticed that my CPU consumes considerably more > > power (an extra 0.5W) when running at the lowest speed > > (1.00GHz) as opposed to when it runs at its native speed > > (2.16GHz); it may be a hardware flaw (ACPI?) or anything > > else, I don't know. > > What driver do you use to modify the clock? > If its clock-modulation, its not good for power consumption (only > for thermal emergency), afaik.
I've tried both acpi and centrino and none of them seems to give any power savings at all (see below). > > > I wonder > > whether cpufreq, in as cool and sexy as it is, does make any > > sense at all (given the fact that it does introduce some > > overhead). For me, it seems that it doesn't (even when I > > adjust the minimum frequency so as to avoid the 1.00GHz > > thing described above). My guess here is that a faster clock > > allows the CPU to do its work quickly, and then sleep > > longer. I may be wrong, and I would like to know whether > > other people experience the same situation. > > Try the ondemand governor. It should make the CPU go max speed, do > the work fast, then go back to low-speed&sleep state. > The cpuidle patch should also help make better use of C-states. I did -- theoretically, I agree that a lower speed and a lower voltage should produce less heat, and consume less power, just that I couldn't measure any reduction in power consumption, so I'm wondering whether other people experience the same situation. are you using cpufreq? do you get much power savings? I think I will also be looking at linux-phc (https://www.dedigentoo.org/trac/linux-phc/) when I've got some time. > > > An idle kernel, for me, > > produces (still in runlevel 1) just ~1 wakeup/second (with > > C3 residency times of ~850-1000ms). > > That should be good enough ;) well, yes, it's good, but not enough: my system still draws about 17-18 watt on idle (a mostly black tty in runlevel 1, only necessary kernel modules, filesystem mounted readonly, no audio, etc.), whereas mac os x gets away with as little as 11 (full functionality, all drivers, and graphic environment). so I'm wondering what causes such a big difference... > > The next steps will be to identify userspace code that > > Try some other hardware tweaks, such as backlight, tv-out-disable, > etc. backlight was dimmed down to a very low level during tests. x11 wasn't even loaded (though the difference between a linux console and x11+vesafb is negligible in my case). everything that wasn't strictly necessary was removed from the kernel, and later loaded as a module to confirm whether each particular module causes increase in wakeups and/or power consumption (an idle snd-hda-intel alone, for example, is responsible for a couple of watts in my case). andrea. _______________________________________________ Power mailing list [email protected] http://www.bughost.org/mailman/listinfo/power
