Re: Centrino question

Cyril Wattebled
2004-05-21T12:56:37Z

Thanks for your answer,

However, I don't understand, I was told that the centrino processor and chipset
supports C3 and even C4.
Why would they intend C3 to be disabled ?
By the way, I tried to change the value of ACPI_PROCESSOR_MAX_C3_LATENCY to
1002 so that C3 is enabled. However, it doesn't change anything, C3 state
is never called.
Actually, I'm looking for a way to make my laptop last longer
unplugged because I think and I also have been told that 2h30 of battery life
is really disappointing for the centrino. Some guys last 3h30 with a P4
3.06ghz, with almost the same battery capacity. I thought that C3 would help a
bit on that but since it's disabled, I don't know what to do. I already enabled
Speedstep, tweaked hdparm spin down value, disabled devices like Bluetooth and
pcmcia.
I so frustrated because I can last up to 6h unplugged on the windows platform
but only 2h30 on linux. There must be something wrong.
Do you guys have any ideas?
Thanks anyway.

--
Cyril Wattebled
neurowork-GANU6spQydw@public.gmane.org

On 20 May 2004 23:50:29 -0400
Len Brown <len.brown-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> wrote:

> On Wed, 2004-05-19 at 21:57, Cyril Wattebled wrote:
> > Thanks for your answer.
> >
> > I have checked why exactly the C3 state is disabled thanks to the
> > information you provided.
> > It seems that it's because the C3 latency is too large. The value is 1001.
> > As the max value is 1000, my question is:
> > Is it safe to change ACPI_PROCESSOR_MAX_C3_LATENCY ?
> > I don't have the knowledge to understand what this latency is about, so I
> > don't really know if 1 microsecond really changes something.
> > So is it the FADT table value that is wrong, if not, what should I do ?
> > Could you give me a hint on that if you have time.
> > Thank you.
>
> 1000 is from the ACPI spec. If the BIOS put 1001 there, then they
> intended for C3 to be disabled. You don't want to touch this.
>
> Indeed, if you were just under 1000, you'd have trouble on 2.6,
> since clock ticks are 1ms apart...
>
> -Len