ACPI C and P states on Conroe

[Joe Harvell <jharvell@dogpad.net>]

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?

---
Joe Harvell