Tuesday, 10 August 2010

Acer Timeline 3810T down to 5.8W with Linux

[ubuntu] Acer Timeline 3810T - Page 90 - Ubuntu Forums
Re: Acer Timeline 3810T
I just found another 1.2W of power saving trick in my 3810T, bringing my minimum power usage down from 7.0W to 5.8W.

Powertop used to show the Intel graphics chip as generating 60 interrupts/second:
51,3% ( 60,0) [i915@pci:0000:00:02.0]
But if I do a Suspend-to-RAM (Fn-F4) and wake it up again the 60Hz interrupt from i915 disappears and my power usage drops 1.2 Watts.

Now, the odd thing is that if I start a new instance of Powertop the 60Hz i915 interrupts returns and power usage goes up by 1.2W again. It seems that Powertop is probing the hardware and triggering the i915 60Hz interrupt.
The i915 interrupts is described on Powertop's homepage http://www.lesswatts.org/projects/powertop/known.php#intelgfx but the documented fix (setting "NoDRI" in xorg.conf) doesn't seem to do anything.

My 3810T is configured as follows:
Ubuntu 10.04 with kernel 2.6.32-24 and backports for wireless and alsa.
Compiz configured to minimum bells and whistles.
Core2 Solo CPU U3500@1.40GHz; Harddisk replaced with Intel SSD.
Fan disabled by disconnecting it from the motherboard. (I'm running a temperature monitor that will hibernate the laptop if it reaches 75°C).

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