Vinay Devadas wrote: > Hi Mark, > > I am Vinay, working on the Turbo Mode RFE on PowerTop. > > So this means that, when a *Turbo Mode supported* processor runs at P0, then > it may actually be running at some frequency *greater than or equal to its P1 > frequency (2400 in the example)*. So using APERF/MPERF will help us determine > the average frequency in P0 for such conditions. Is that correct ? >
Yes, I believe that is correct. Mark > Thanks, > Vinay > > ----- Original Message ----- > From: Mark Haywood <Mark.Haywood at Sun.COM> > Date: Wednesday, July 23, 2008 12:21 pm > Subject: Re: [tesla-dev] Question on PowerTop V 1.1 > To: Eric Saxe <Eric.Saxe at Sun.COM> > Cc: Vinay Devadas <Vinay.Devadas at Sun.COM>, tesla-dev at opensolaris.org > > > >> Eric Saxe wrote: >> >>> Mark Haywood wrote: >>> >>>> No. When it runs at P0, then the minimum frequency it will operate >>>> >> at >> >>>> is 2400MHz. But it is very likely to run faster than that and yes, >>>> >> I >> >>>> believe it may even run faster than 2401MHz. So, the "average >>>> frequency" as far as I know is the average speed while in P0. I >>>> believe that the APERF/MPERF registers will be used to determine >>>> >> the >> >>>> average frequency. But I'm not working on that, so maybe I should >>>> >> let >> >>>> someone else answer that. ;-) >>>> >>>> >>> Is it the case here that there's essentially two "P0" states being >>> enumerated by ACPI (One for turbo mode enabled, and one for disabled)? >>> >> It depends what you mean by P0 states. By definition, P0 is the first >> >> P-state returned when evaluating the _PSS. The P0 frequency for Turbo >> >> Mode enabled systems is always supposed to be defined as the P1 >> frequency + 1MHz. >> >> If you were to disable Turbo Mode (assuming the BIOS gives you the >> option), then I believe you would find your supported_frequencies_Hz >> to be: >> >> 800000000:1200000000:1600000000:2000000000:2400000000 >> >> Why did Intel define the Turbo Mode P-state P0 this way you ask? I >> suspect that they did it this way so that an OS could basically >> support >> Turbo Mode without any modifications. An OS that is totally ignorant >> of >> Turbo Mode will still request Turbo Mode (by requesting P0) when the >> CPUs are heavily utilized at P1 (not yet over clocked). That means >> existing Windows, Linux and other OSes that have been in the can long >> >> before Turbo Mode existed can still take advantage of it. >> >> >>> This is what the cpu_info kstat is showing on Kuriakose's laptop >>> (thanks Vinay): >>> >>> supported_frequencies_Hz >>> 800000000:1200000000:1600000000:2000000000:2400000000:2401000000 >>> >>> I'm wondering what the essential difference is between the 2400 >>> >> state >> >>> and the 2401 state (besides 1 MHz, and i'm guessing that's not even >>> >>> the difference)... >>> >> The 2401 state says feel free to run 2400 or faster if conditions allow. >> >> Mark >> >> >>> Thanks, >>> -Eric >>> >> _______________________________________________ >> tesla-dev mailing list >> tesla-dev at opensolaris.org >> http://mail.opensolaris.org/mailman/listinfo/tesla-dev >> > _______________________________________________ > tesla-dev mailing list > tesla-dev at opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/tesla-dev >
