We participate in the BOINC CUDA project to use idle CPU and GPU time for scientific research purposes.
We recently updated to the newest NVIDIA drivers for Windows 7 x64 which are version 270.61.
After doing this we noticed the core clock on our NVIDIA Geforce 480 would drop from a standard or overclocked speed, down to 405mhz. The core clock would stick there and the only way we can get it back is to reboot that machine. Then after a few minutes again running the BOINC app, the core clock would drop to 405mhz again. (We can see this because we use the MSI Afterburner 2.1 app, which has a nice real-time graph that shows current clock, memory and GPU utilizations among other things and also allows you to overclock the card.)
It turns out that there is some new “feature” (or bug) in the NVIDIA v. 207.61 drivers that is causing this issue.
Our solution was to uninstall the 270.61 drivers, restart and then install v266.58 drivers (which are the ones that preceeded 270.61).
After a reboot and more testing the core clock speed stay at the factory default speed (700mhz) or at our designated overclocked speed, without ever dropping down to 405mhz.
Apparently this is a widespread issue and users playing 3D based games also experience this issue as dropped frame or sluggish framerates while gaming… those users should also think about reverting to 266.58 until NVIDIA gets this sorted out.
We’ll have more information after we test the next version of NVIDIA’s drivers.
UPDATE 06/22/2011: The same “clock drop” is also experienced on the most current NVIDIA 275.33 drivers. Don’t use those if you plan on using CUDA.