On Tuesday 30 January 2007 12:35, Joe Harvell wrote:
> I am trying to enable all the power saving features I can on my Conroe
> E6600. After much searching on the web, I am a little confused about
> the Linux kernel support for ACPI on the Conroe.
>
> Here is my setup:
> Intel Core2 Duo E6600
> Asus P5-B Deluxe board (Intel P965).
> I am running a Gentoo kernel based on 2.6.19.4.
>
> I have managed to enable EIST using cpufreq with the speedstep-centrino
> driver. But my understanding from browsing the ACPI spec is that this
> is still within C0, i.e. not much power savings.
Right, P-states are effective only when code is executing,
and on this processor (with C1E) will have no effect on idle power.
> Here are my questions:
>
> 1) For P states, which cpufreq driver should I be using? I've heard
> speedstep-centrino is deprecated (but only some aspects of it) that are
> being moved into acpi-cpufreq. But I can't get acpi-cpufreq to load in
> my kernel version.
In 2.6.19 I believe that speedstep-centrino is the one to use.
The transition to acpi-cpufreq happens in 2.6.20.
> Also, I would have thought speedstep-ich would be
> the driver, just based on the name.
Don't use speedstep-ich.
> How do I know (other than trying
> all modules to see which one loads) which one I should be using?
> 2) What kind of support for C1-C3 does the Conroe have? The ACPI spec
> says C2 and C3 require chipset support on the motherboard. Does P965
> have that. Does it matter between boards (e.g. P5B)?
I believe that Conroe currently supports just C1 --
this is true for the ones I have.
Internally it is an "Enhanced C1" called C1E where the voltage is reduced
in C1-- but this is transparent to software, which thinks it is just C1.
You can observe this in
/proc/acpi/processor/*/power
> 3) What versions of the kernel support C1-C3 states? What kernel
> options are germane to this? What libraries/tools are involved?
C1-C3 have been supported for a long time.
2.6.20 adds a few tweaks to use a more efficient implementation,
but you'll not notice a difference on today's desktop processor.
cheers,
-Len
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