Arch Linux

gobeav3rs297

Member

From: Portland Oregon

Registered: 2007-11-06

Posts: 60

powertop + c-states

Hi,

I've a laptop with a Core2Dou T5600 cpu and i've been using powertop to try to measure my battery power usuage and noticed from powertop that under linux my laptop can only go to C4 doesn't exist because it only lists C0, C1, C2, and C3 as the max.  Under windows however when i use rmclock to manage my cpu it could go to C4.  What's the reason for this?

Vincent

big_gie

Member

Registered: 2005-01-19

Posts: 637

Re: powertop + c-states

I was reading this from powertop's site:

I see only C0, C1, and C2. Why don't the other C-states show?

It's mostly a BIOS thing. Some BIOS hide C3/C4 when on AC power, and others show only C3 which is really a C4 underneath when on battery. Note that the 'max_cstate:C8' value in /proc/acpi/processor/*/power tells the maximum number of C-states the Linux kernel can handle, not the number of C-states implemented in your hardware.

gobeav3rs297

Member

From: Portland Oregon

Registered: 2007-11-06

Posts: 60

Re: powertop + c-states

ahhh i see, thanks.  I dual boot, so windows when using the battery the lowest power usage i got was around 7-8W but on linux it seems like i doesn't go any lower than 11W so that why i was worried that the C3 states was wasting so much power.  So is linux just not every good at power management unlike windows?

Vincent

big_gie

Member

Registered: 2005-01-19

Posts: 637

Re: powertop + c-states

So is linux just not every good at power management unlike windows?

That's a hard question...

In linux, you (may) know what eats up your power. Windows is a blackbox, so you can't know what's happening.

Linux has its drawback. But what makes it wonderful is that its always getting better. Intel's initiatives (lesswatt.org) is really helpfull. So if you use a recent kernel (2.6.21 for x86 and 2.6.24 for x86_64), the dyntiks lowers your power consumption.

Arch is great for that, you get the newest packages quite early.

gobeav3rs297

Member

From: Portland Oregon

Registered: 2007-11-06

Posts: 60

Re: powertop + c-states

Thanks big_gie, you're a real help, and yes lesswatt.org is awesome.  I've been going there this past week and just trying out all the tricks to optimize my laptop and it is very helpful and bring the numbers down.  Just not as much as windows but that's alright,I still like Linux better than windows even though i've only been using linux for about 2 months now. 

Vincent