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Re: ACPI with AMD64

On 2/11/06, Thimo Eichstaedt <abc@digithi.de> wrote:
> Hi,
> after some time of searching in  the acpi mailling lists I've found
> the following message:
> http://article.gmane.org/gmane.linux.acpi.devel/16431
> So it seems as if these states are disabled by the mainboard
> manufactures, great!
I thought that since my motherboard (Asus A8N-E) supports Cool&Quiet,
it will have at least C2 enabled. I was wrong. IMHO there should have
been a BIOS option to turn it on/off, but there isn't. I updated the
BIOS to the latest (1010), but it still says throttling and C2 isn't
(I understand why they ship motherboards with C2 turned off, it is
said it hurts performance)

I had a similar situation with an AthlonXP + MS8188E motherboard, but
there were programs that could enable C2 support (fvcool, athcool,
etc.). It had a little impact on performance (IDE performance), but
there I had to use C2, otherwise my CPU would have been too hot.

I looked at those programs again, they support nforce2, but nothing is
said about nforce4. I could try to enable C2 by telling these programs
that my chipset is nforce2, but it would probably break something, as
in nforce4 those registers might be somewhere else.

There could be a workaround for enabling C2: you could try to change
the ACPI_PROCESSOR_MAX_C2_LATENCY in include/acpi/processor.h, and
recompile the kernel. However without enabling C2 on the motherboard I
doubt it will have any effect. That limit is there with a purpose.

Did anybody succeed in enabling C2 on a motherboard with nforce4 chipset?

However on my Athlon XP I had throttling even without using athcool
(if I recall correctly).
Why isn't throttling supported on the Athlon64? Is there a way to enable it?
How does the kernel detect if throttling is available?

> root <at> porygon:~/# cat /proc/acpi/fadt |acpitbl |grep P_LVL
> P_LVL2_LAT:       190
> P_LVL3_LAT:       1900

P_LVL2_LAT:       101
P_LVL3_LAT:       1001

> If you will see more than 100 in the first line and more than 1000 in
> the second one, your
> Cx states are blocked by BIOS.

Yeap, it is blocked by BIOS.


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