Extreme CPU usage while GPU rendering? For GPU rendering I use a GT 650 Ti Boost. Strangely, rendering jobs consume all my CPU time so anything else I do on the computer is just as choppy as when I do a CPU render.

I have Blender configured to use 6 of 8 cores when it does use the CPU but that doesn't help either. It's an FX8350 CPU, with 8 gig of RAM, so that should be lots of horsepower too.

Since there are guides for setting up multiple instances of Blender to handle GPU/CPU renders on alternate frames I would expect the CPU to remain largely free during a GPU-only render.

Does anyone have insight/tips as to why it's sucking up more resources than it probably should?
I'm certainly no expert, but I had a 95% CPU usage whilst rendering, even though I had chosen GPU Compute from the Render section.  What I didn't realise, was that I also need to select CUDA in User Preferences/System too.  After that I re-did the same Render and the CPU then hovered around 15% as expected.  V 2.79 if that makes any difference.  Will be interesting in the forthcoming version of Windows which supposedly will show the GPU usage in the Task Manager.