Measurements: Massive Display-related power savings

[Harald Welte]

Hi,

On Wed, Oct 08, 2008 at 07:58:43PM +0100, Andy Green wrote:
 
> > same using manual "deep-standby" into jbt		 82mA
> > same plus disabling glamo DCLK pixel clock		 59mA
> 
> Wow that last 23mA is surprisingly large, it's like 80mW.  

it's actually not too surprising.  According to the power consumption analysis
we got for the glamo3372 (it's in /space/docs internally), there should be
about 60mW difference.  Since we run the glamo at even higher clock rate,
our absolute power consumption (and thus the gains of disabling parts) is going
down.

I think the major point is not actually the lack of having to generate the LCM
signal, but the 100% reduction in glamo-SDRAM use.  Screen refresh of 640x480
at 60Hz (or whatever we use these days) puts a very high constant load on the
SDRAM..

> Just to be clear these were already all down in suspend, these new savings
> come in the case where you're not in suspend but the display is "off".

Yes.  And once people start to use their GTA02s for something else than just a
regular phone (i.e. run actual applications for GPS data logging, music players
or whatever other creative things that 'openmoko is all about'), this 'display
off but cpu running' state will be much more predominant than today, where you
juts simply don't have that many of those applications...

Cheers,
-- 
- Harald Welte <laforge at openmoko.org>          	        http://openmoko.org/
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