[mythtv-users] Improving Power Consumption on ASUS M3N78 Pro NVIDIA 8300 Chipset

Michael T. Dean mtdean at thirdcontact.com
Tue Aug 4 15:52:13 UTC 2009


On 08/04/2009 08:01 AM, David Knight wrote:
> My minimum clock speed on the MythTv box is set to 1800000 due to issues
> with VDPAU when running at 1000000. however this only knocks 5-10w off the
> total.

Out of curiosity, have you actually calculated how much wattage the use 
of VDPAU saves you?  If, for example, you run the MythTV box 24/7, then 
you're running at 5-10W extra all day long just so you can use VDPAU 
sometimes.  So, that means you're using an 120Wh to 240Wh each day 
compared to configuring the system to allow frequency downscaling.

Now, let's say you watch 2 hours of TV per day.  That would mean VDPAU 
would have to save you 60W to 120W compared to software decoding with 
the CPU to make up for the wasted power used by funning at full clock 
all day.  Even if you watch 4 hours of TV per day, you're still looking 
at VDPAU's needing to save you 15W-30W over software decode.  And, when 
you factor in that you'd likely be watching TV with various encodings, 
even if the maximum benefit is in the range, it still may not make up 
for the day's wasted power from not downscaling frequency.

Have you considered just not using VDPAU?  Or, if you feel you must use 
VDPAU, can't you just make sure that when mythfrontend is started, it's 
started by a script that sets the governor to Performance and when it's 
exited (back to MythWelcome), the script sets the governor back to 
Conservative?

Mike


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