Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 3 Feb 2003 21:18:06 +0000 | From | Dave Jones <> | Subject | Re: CPU throttling?? |
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On Mon, Feb 03, 2003 at 01:14:18PM -0800, Grover, Andrew wrote:
> 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.
Most (all?[1]) other modern x86 mobile processors behave the way I mentioned. AMD Powernow (K6 and K7), VIA longhaul/powersaver all have optimal voltages they can be run at when clocked to different speeds. By way of example, a table from my mobile athlon..
FID: 0x12 (4.0x [532MHz]) VID: 0x13 (1.200V) FID: 0x4 (5.0x [665MHz]) VID: 0x13 (1.200V) FID: 0x6 (6.0x [798MHz]) VID: 0x13 (1.200V) FID: 0xa (8.0x [1064MHz]) VID: 0xd (1.350V) FID: 0xf (10.5x [1396MHz]) VID: 0x9 (1.550V)
Sure I *could* run that at 523MHz and still pump 1.550V into it, but why would I want to do that ?
Dave
[1] Unsure about the crusoe.
-- | Dave Jones. http://www.codemonkey.org.uk - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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