The ati petition

[Mathieu Lacage]

On Mon, 2004-09-06 at 02:23, Vladimir Dergachev wrote:
> >>> to the same power-performance tradeoff for your graphics card and saving
> >>> power.
> >> Good point. I would imagine that since most of GPU is inactive under
> >> regular X drivers I am running at minimum power ;)
> >
> > Unlikely.  I suspect that, like with the CPU, the GPU speed must be
> >  manually slowed.
> 
> Unlike regular CPU, GPU consists of many blocks. I would expect that if 3d 
> engine is not used at all it consumes little power - kinda like running 
> HLT continuously on spare CPU.

Actually, that is pretty unlikely. A lot of the power consumption of
these devices (even when they are running at full speed) comes from the
clock tree which distributes the clock throughout the chip. Unless the
designers have added special multiplexers to stop completely the clock
tree of the unused blocks, these will consume a lot of power even idle.
The basic clock rate used nowadays is high enough and the area of the
chip die is big enough that these issues are non-negligeable. Of course,
restarting the stopped blocks can also be a bit tricky for the chip
designers.

Another rather popular technique is to step the clock speed but that is
much more complex to implement for the designers which is why few ASICs
really do it.

Of course, this is off-topic but I could not resist. Bad bad me. It
should be said I have minimum experience in this domain so, the usual
disclaimers apply.

regards,
Mathieu
-- 
Mathieu Lacage <mathieu at gnu.org>