[mythtv-users] Is the GT220 the new chip of choice? (Idle power?)

[Jarod Wilson]

On Oct 23, 2009, at 3:30 AM, Andre Newman wrote:

> Having to turn off cpu speed changes to keep VDPAU fed at full  
> bandwidth negates any other benefits for me right now, I need to  
> find where in MythTV to change the CPU speed profile when playback  
> starts and then revert it at the end.


MythTV doesn't do anything to change the cpu speed profile. The  
*kernel* controls that on any modern system. (And on less modern ones,  
its a userspace daemon called 'cpuspeed'). The cpu frequency scales  
with demand, and the thresholds where scaling happens are entirely  
tunable. Simply alter the idle/busy thresholds at which the cpu freq  
governor (typically 'ondemand' these days) ramps up the clock speed.

The main place of interest is /sys/devices/system/cpu/cpu*/cpufreq/ 
ondemand/up_threshold.

For some distributions, there's an init script that sets up cpu freq  
scaling on boot, and you can override the defaults by way of a config  
file. Others may require rc.local dickery.

See also the kernel documentation that covers all this in <kernel  
source>/Documentation/cpu-freq/

-- 
Jarod Wilson
jarod at wilsonet.com