[tlug] Laptop power consumption

[Marco Toldo <marcoxtoldo@example.com>]

Hi,

I know power consumption in Linux is still an open problem, but I'm
trying to figure out where such consumption on my laptop comes from.

I've got a 6-months old Samsung R520 notebook with Intel Core Duo, 250
Gb SATA disk, 4 GB Ram and ATI Radeon HD 4300 gpu, with opensuse 11.3
as only OS on the machine (..bought with windows vista pre-installed
but completely removed without even booting it once)

According to manufacturer's declaration, battery should last
approximately 210 min. Obviously I guess this could be achieved with
windows-based os only, but BIOS has some features for "Other OS" so I
could expect a reasonable battery lifetime under Linux too.  However
reality is really different...battery has a mere lifetime of
approximately 1 hour, with an unbelievable consumption around 20 W.
I thought this could be caused by the heavy load of opensuse, so tried
to be more "gentle" with an ubuntu 9.10 live cd (...thinking a live cd
could be at least more lightweight as it doesn't load all drivers) but
I got just 5 min of additional battery.

I've already tried any kind of possible optimization (the 20 W
consumption comes with lowest screen brightness) thanks to the hints
of powertop (an utility for Intel cpus giving a brief overview about
which tasks are waking up cpu too much) but I was able to increase
performances to a mere 19 W.

Since cpu is already optimized by kernel (frequency scaling, etc...)
with a reasonable amount of interrupts (ranging between 50 and 130 per
second), I think the "guilty" is the Radeon gpu. Amd provides a
proprietary driver for this (supposed to have better perfomances) but
it doesn't work as well as the open one, with no enhancement in power
consumption (moreover, although latest version should be optimized for
opensuse 11.3 and ubuntu 10, it cause a segmentation fault and X can't
be loaded).
Googling around the web I found high consumption could be generated by
a bug in DRI, so I modified xorg.conf with 'Option "NoDRI"' in
'Driver' section (actually I don't need 3D at all).
While number of interrupts decreased significantly (constantly below
50 per second),  consumption is stalled to 18.6 W, definitely too high
:-(

Now I'm thinking about trying ubuntu netbook remix, hoping this may
have some built-in magic to extend battery life. I'm not interested in
the "I don't believe it"-10 hours battery of Mac books (...damn it if
it's true), but I would really love my laptop if it could get at least
2 hours...

I know many people have same problem, with a power consumption around
20 W, but hope some of you guys can have any hint (or know any distro)
to solve this.

Cheers,

Marco