Fwd: macbook pro & powertop

[a.biardi at tiscali.it]

On Tuesday 17 July 2007, Guillaume Pujol wrote:

> Sorry for the double mail Andrea, this was supposed to be on list
> (this is early in the morning here :/) ...
>
> ---------- Forwarded message ----------
> From: Guillaume Pujol <guillp.ml at gmail.com>
> Date: 17 juil. 2007 07:28
> Subject: Re: macbook pro & powertop
> To: "a.biardi at tiscali.it" <a.biardi at tiscali.it>
>
> 2007/7/17, a.biardi at tiscali.it <a.biardi at tiscali.it>:
> > well, yes, it's good, but not enough: my system still draws about
> > 17-18 watt on idle (a mostly black tty in runlevel 1, only
> > necessary kernel modules, filesystem mounted readonly, no audio,
> > etc.), whereas mac os x gets away with as little as 11 (full
> > functionality, all drivers, and graphic environment). so I'm
> > wondering what causes such a big difference...
>
> The difference may come from the GPU (Radeon X1600 Mobility), which
> oddly doesn't support powersaving under Linux (to be more specific,
> the binary blob from ATI doesn't support that feature). This
> results in the GPU always being at its full power, about 8 to 10W.
> This behaviour only happens on the MacBook Pro Core2Duo from
> november 2006 (maybe other laptops as well).
> See http://www.phoronix.com/forums/showthread.php?t=3130

yes, that's exactly the model I have; I'm aware of that, and have 
stopped using the crappy fglrx long ago (and you can bet I will never 
buy a laptop with an ati card anymore). I used vesafb for a while (I 
don't need any fancy 3D stuff), then I'm currently using the 
development version of xf86-video-avivo 
(http://gitweb.freedesktop.org/?p=avivo/xf86-video-avivo.git), which 
does the job, but being based on reverse engineering of the binary 
stuff from amd, it will still take a long while to have powersaving 
features built in (but at least there's some source code, I could 
probably look into that and play with some registries).

that said, do you think that a GPU can account for as much as 8 to 
10W? isn't that too much?

I'm happy about the number of wakeups per second, can keep them at a 
very low rate, even under X; I'll get myself to work on some kernel 
timers and some GUI applications that seem to abuse gtk timers, 
because I believe I can save a few tenths of watts and reduce heat as 
well.

I also downloaded datasheets from intel for my chipset, to confirm 
whether the current kernel implements all available powersaving 
techniques, as time permits.

but, still talking about cpufreq, does your own system show a big 
difference in power consumption when it runs at a lower 
clock/voltage? according to intel's specs, my cpu (T7400) works with 
the following voltage ranges:

highest frequency: 1.0375-1.3000V
lowest frequency:  0.7500-0.9500V

that alone, to me, says that there may be quite a lot less heat and 
power consumption at lower frequencies/voltages.

also, still according to the cpu datasheet, DC amps range all the way 
from 26.7A (both cores in C1) down to 9.9 (both cores in C4 enhanced 
deeper sleep), so that also should make a huge difference, or not? 
where am I wrong?

andrea.