Messages in this thread | | | From | "Grover, Andrew" <> | Subject | RE: CPU throttling?? | Date | Mon, 3 Feb 2003 13:51:13 -0800 |
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> From: Dave Jones [mailto:davej@codemonkey.org.uk] > > 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 ?
Voltage scaling. Yes, it's widespread. I was referring to an additional capability to lower voltage while the CPU is sleeping. But I digress.
But this whole thread didn't start as a discussion of voltage scaling, it started as a discussion of throttling - e.g. keeping your system at 1400MHz 1.550V and simulating a slower processor by toggling the STPCLK# pin. And you're exactly right that no you *wouldn't* want to do that.
I think we are in agreement. ;-)
Regards -- Andy - 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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