5950x + 17.2 - Very Low CPU Usage! -

Hi Everyone!
I've just switched from 16.2 to 17.2. Free version.
CPU utilization during rendering using my x5950 cpu were as high as 70%. now it doesnt get over %5 and rendering time are way too long.
I haven't found any option to disable GPU rendering and switch to CPU-only (if such thing exists of course).
I am also getting GPU Error Code -59. My GPU is GTX 680 and I started to get this error after I updated to the latest Geforce driver, hoping to fix my low cpu usage problem.
I searched for solution before posting this but havent found any useful posts.
I've just switched from 16.2 to 17.2. Free version.
CPU utilization during rendering using my x5950 cpu were as high as 70%. now it doesnt get over %5 and rendering time are way too long.
I haven't found any option to disable GPU rendering and switch to CPU-only (if such thing exists of course).
I am also getting GPU Error Code -59. My GPU is GTX 680 and I started to get this error after I updated to the latest Geforce driver, hoping to fix my low cpu usage problem.
I searched for solution before posting this but havent found any useful posts.