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 ? Thanks, Vinay ----- Original Message ----- From: Mark Haywood <[email protected]> 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
