Why is Gutsy so hungry for power?

[Liam Proven]

On 05/01/2008, Marius Gedminas <marius at pov.lt> wrote:
> On Thu, Jan 03, 2008 at 08:28:29AM -0800, John Leonard wrote:
> > Does anyone know why Gutsy uses more power than Feisty
> > and how consumption can be reduced?
>
> I think the correct question to ask would be "why Gutsy uses more power
> than Feisty on that particular hardware", and I would like to know the
> answer as well.

There are also lots of users discovering that Vista uses a lot more
battery power than XP. The main reason for this - and it may also
apply to 7.10 - is that Vista's UI uses a machine's 3D graphics
accelerator for display compositing. XP does not. Similarly, 7.10 has
Compiz on by default, which again uses 3D to do window composition.
7.04 has this as an optional feature which much be manually enabled.

A 2D GUI does not use the 3D part of a graphics accelerator at all.
Mobile graphics chips in particular are often designed so that large
parts of the graphics subsystem are not used at all when in 2D mode.
Whereas a modern graphics subsystem may have 256MB of video RAM or
more - up to 3 or 4 times that - which is all used in rendering 3D, a
simply 1280*1024 desktop uses a tiny fraction of that for the
framebuffer:
1280 * 1024 pixels = 1,310,720 pixels
1310720 * 3 bytes per pixel for 24 million colours = 3,932,160 bytes
3932160 / 1024 = 3,840 kB
3840 / 1024 = 3.75 MB

Under 4MB of RAM for a megapixel display. Compare this to a modern
very low-end 128MB graphics card. That's 124MB of video RAM wasted
when in 2D mode. All that RAM takes power.


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