Messages in this thread |  | | Subject | RE: CPU throttling?? | From | Seamus <> | Date | 04 Feb 2003 10:22:08 +0000 |
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On Mon, 2003-02-03 at 21:14, Grover, Andrew wrote: > > From: Dave Jones [mailto:davej@codemonkey.org.uk] > > Valdis.Kletnieks@vt.edu wrote: > > > > > It's conceivable that a CPU halted at 1.2Gz takes less > > power than one > > > at 1.6Gz - anybody have any actual data on this? > > Alternately phrased, > > > does CPU throttling save power over and above what the halt does? > > > > Given that most decent implementations scale voltage as well as > > frequency, yes, a lower speed will save more power. > > You save the most power when the CPU is at the lowest voltage level, and > in the deepest CPU sleep state (aka CPU C state). > > Throttling offers a linear power/perf tradeoff if your system doesn't > have C state support (or if you aren't using it) but really it is > preferable to keep the CPU at its nominal speed, get the work done > sooner, and start sleeping right away. The quote above makes it sound > like the voltage is scaled when throttling, and that isn't accurate - > voltage is scaled when sleeping (to counteract leakage current), at > least on modern Intel mobile processors. > > Valdis, you may want to try compiling in ACPI and ACPI Processor support > in 2.5.latest and see what happens to your battery life (if you haven't > tried already). (A caveat - ACPI still doesn't work for everyone, but if > it does, you should see a power savings.) > > Regards -- Andy
Hmmm, it seems most of these apply to mobile processors. I'm using AMD 1.4 Athlon Thunderbird on a desktop, as you know my processor was the one before release low power AMD XP processors. It uses a savage amount of power, and operates well into 60 and 70 degrees celcius.
I'm not a big linux head, can someone through me an ACPI link, related to this issue of CPU C state?
One other thing, apart from saving power on CPU and hard-disk (via hdparm) is there anything else I can look into ? something worthy though.
Thanks,
Seamus
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