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-   -   Disabling power saving features (http://www.nvnews.net/vbulletin/showthread.php?t=89968)

shaundennie 04-18-07 09:48 AM

Disabling power saving features
 
Is it possible to disable/modify the power savings functionality of the Go series cards (7900GS Go in my case) so that they don't underclock when the GPU is relatively idle? I'm sure it's very useful for power savings to have GPUCurrentClockFreqs scale down to 100,100 but, it's very bad for composited desktops because it often takes some time for the card to realize that it needs to step back up to maximum speed. Because of this there is frequently a "warmup" period where everything is updating at like 5 frames per second when using things like compiz scale/switcher/cube (specifically when dealing with large windows) until the card wakes up and goes to full speed.

I've looked around for a way to disable this functionality but, I didn't notice anything. Having a writable "GPUMinimumClockFreqs" or something of that nature would be ideal because it would allow people to use laptop_mode to control the power savings features. As it currently stands, it's painful to use a composited desktops because the card is generally in low power mode and so any sort of large screen update is exceedingly slow.

stefan42 04-18-07 01:01 PM

Re: Disabling power saving features
 
I once asked NVIDIA because in my case the screen flickers when the clock frequency changes (also a 7900 Go GS), and Lonni Friedman from NVIDIA told me "No, that isn't possible via any direct means. You could try using Coolbits to downclock the GPU though."

Anyway what worked is adding "options nvidia NVreg_RegistryDwords="PerfLevelSrc=0x2222" to /etc/modprobe.d/options. My GPU will not downclock then. But it's completely unclear what other effect this setting has or what it's meant to solve ;-) so be warned. In my case the screen is garbled after a X restart.

shaundennie 04-19-07 08:44 AM

Re: Disabling power saving features
 
Quote:

Originally Posted by stefan42
Anyway what worked is adding "options nvidia NVreg_RegistryDwords="PerfLevelSrc=0x2222" to /etc/modprobe.d/options. My GPU will not downclock then. But it's completely unclear what other effect this setting has or what it's meant to solve ;-) so be warned. In my case the screen is garbled after a X restart.

I'm giving this a shot now. After a lot of reading it looks like this setting also helps with the random lockups that cause the Xserver to stop responding (to the point where Ctl-Alt-Backspace won't kill it). If that's the case, it may be worth dealing with the extra heat generated by not letting the card drop down to a power saving mode.

shaundennie 07-04-07 11:06 AM

Re: Disabling power saving features
 
I've recently updated to 100.14.09 and it's extremely painful on laptops with a compositing window manager. It seems that now the GPU essentially refuses to clock up to full speed when doing intensive compositing things (scale/rotate/switcher). Even doing something like rotating the cube with the keyboard continuously for 15 seconds doesn't cause the GPU to speed up. In fact, the only way I can reliably cause the GPU to speed up is to do an "nvidia-settings -q all" in a terminal. It does appear that it scales the GPU down at a slower pace after it's been forced to full speed but, I never timed it before so it could be my imagination.

Is there any way to fix this? My laptop with an i915 GPU now has a much smoother compiz experience than my 7900GS.


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