Subject: Re: speedstepping on amd64 - why not?
To: Juan RP <juan@xtrarom.org>
From: Tonnerre LOMBARD <tonnerre@bsdprojects.net>
List: tech-kern
Date: 04/22/2007 11:11:56
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Salut,

On Sun, Apr 22, 2007 at 03:57:32AM +0200, Tonnerre LOMBARD wrote:
> dev.cpu.0.freq: 1997
> dev.cpu.0.freq_levels: 1997/-1 1747/-1 1497/-1 1248/-1 998/-1 748/-1 499/-1 249/-1
> dev.acpi_throttle.0.freq_settings: 10000/-1 8750/-1 7500/-1 6250/-1 5000/-1 3750/-1 2500/-1 1250/-1

Apparently, FreeBSD retrieves the list of possible frequencies through ACPI
and also uses ACPI to manipulate them, because it has been a while since
Intel released voltage specifications for all of their CPUs. There is a
ACPI throttling driver, but porting this would probably mean a lot of work
(Which we will have to go through, maybe, but later).

I wonder if there's a way to measure the currently used CPU voltage under
FreeBSD? If so, then I could just add a frequency table for my CPU for the
time being. (If I have to manipulate the kernel to output the CPU frequency,
that's fine too.)

Any hints?

				Tonnerre

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