[Intel-gfx] OT: Power metering [Was: Re: [PATCH] add LVDS downclocking support]
Steven J Newbury
steve at snewbury.org.uk
Tue Mar 24 07:04:23 PDT 2009
On Mon, 2009-03-23 at 19:35 +0100, Erik Andrén wrote:
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> Peter Clifton wrote:
> > On Mon, 2009-03-23 at 00:30 +0000, Steven J Newbury wrote:
> >>> 
> >>> http://www.alamaison.com.au/p/361923/voltcraft-plus-energy-monitor-3000.html
> >> I'm not surprised you didn't see any change measuring power usage at the
> >> outlet. Laptop power supplies are rarely switched mode, and typically
> >> provide their full rating while in use. They aren't typically designed
> >> with energy efficiency in mind.
> > Actually, this isn't correct. Every laptop PSU is almost certainly a
> > Switched mode unit, as is every PC PSU since probably the AT days.
> I'm not doubting your expertise in this area but I've successfully
> measured other power savings on my laptop using the same setup. It
> might not give me the exact measurement but at least a hint on where
> things are heading and I can't detect anything that this patch
> improves the power efficiency of this laptop.
Then it probably isn't working as advertised. AFAIK to get power saving
from LVDS downclocking the display must be idled in much the same way as
CPU idle states. Last time I tried this with an earlier patch on 965GM,
it just locked up. I'll try this patch out and see if it does anything
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