ACPI C and P states on Conroe
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.
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. Also, I would have thought speedstep-ich would be the driver, just based on the name. 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)?
3) What versions of the kernel support C1-C3 states? What kernel options are germane to this? What libraries/tools are involved?
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Joe Harvell
Quoted 4 lines · Joe Harvell
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.
Quoted 8 lines
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.
Quoted 6 lines
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.
Quoted 2 lines
Also, I would have thought speedstep-ich would be
the driver, just based on the name.
Don't use speedstep-ich.
Quoted 5 lines
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
Quoted 2 lines
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