Processor is almost never in C1 state

[dogshu <dogshu-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Hello,

I have a Toshiba Portege laptop with a 500 mhz pentium-3 mobile CPU. 
The processor is almost never is in the C1 state, and spends 99.9% of
the time in the C2 state, even when doing heavy processing.

After a night of compiling KDE, and while running the "burnP6" program
included in the "cpuburn 1.4" package, this is the output of
/proc/acpi/processor/CPU0/power:

active state:            C2
default state:           C1
bus master activity:     00000000
states:
    C1:                  promotion[C2] demotion[--] latency[000] usage[00009710]
   *C2:                  promotion[--] demotion[C1] latency[001] usage[12232108]
    C3:                  <not supported>

As you can see, even though the processor is being maxed out by
burnP6, it remains in the C2 state and doesn't really use the C1 state
at all.

I don't mind having the CPU in this lower power/lower performance
state most of the time... however I occassionally like to play DVDs on
this laptop, and I need all the CPU power I can get when playing DVDs,
or else  I will get lots of dropped frames.

I am running kernel 2.6.10-rc2-mm4.  I noticed that in the kernel
parameters I can disable the C2 state altogether, but I'd rather not
have to reboot whenever I play a DVD.  Is there a way to tweak ACPI so
that the processor spends more time in the C1 state, without giving up
the C2 state entirely?

thanks for any help,
Jim Faulkner


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