Locking frame rate on GeForce FX 5950 Ultra


I’m trying to lock an application to run at a fixed 30Hz update rate on an NVidia GeForce FX 5950 Ultra card. I believe I need to use the wglSwapIntervalEXT() function (as mentioned on previous topics). However, if I set the screen refresh to 60 Hz and call this function with a swap interval of 2 then I still get an update rate (using FRAPS) of 60Hz - I call wglGetSwapInterval() and it returns 2. If I set the interval to 0 it does disable the wait for VSync and if I set it to 1 I get 60Hz as expected.
I believe this should work on this card but as yet have had no joy. I’m using the latest drivers 66.93.

Anybody got any ideas?


Is fraps accurate on this very case ? Do the fps count yourself, or use a crazy value (such as 20 for 3 fps) you should see if it works as intended.

Swap interval worked fine in my gf3 and gf6800.

I don’t think the swap interval does more than wait ‘n’ refresh rate intervals before swapping the buffers… that doesn’t mean the frame rate is less for that (you just don’t see the buffer till it’s swapped, and the thread gets paused)…

Not sure how FRAPS reads the FPS though… if it hooks on the bufer swapping, it then -should- read just 30FPS.

Have you tried making it very high (so that your application is -obviosuly- not running at 60fps), and measure with FRAPS?

I have used an alternative fps count method and also used extreme values and I still get 60Hz update rate. The get function reports back that the swap interval has been set but there seems to be no effect.

What’s the value of the vsync in the control panel->display->settings->advanced->GeForce… tab?
There you can choose between on, off or application respectively. Try to set it to ‘application’ or ‘always off’.


Yep, tried all settings, no effect. I feel there should be a setting somewhere that would kick things into life but not so far.

Driver bug. You’ve done everything correctly.

Seems to be.

Was using the latest 66.93 from NVidia, but if I go back to 61.76 it seems to work fine! Grrr…

Thanks for your help.

66.93 are riddled with bugs. They lock up HalfLife2 in my experience…unforgivable. And they’re still up on the nvidia website as the latest stable consumer build.

Oh good, so I’m not the only one w/ loads of problems with these drivers. The 75.xx drivers should be out soon though.