Have a look on the video at 57 seconds it's there.
This is another way to do the same thing, mod it for your own preferences.
"gpu_threads_conf" : [
{ "index" : 0, "intensity" : 800, "worksize" : 8, "affine_to_cpu" : false, "strided_index" : true },
{ "index" : 0, "intensity" : 800, "worksize" : 8, "affine_to_cpu" : false, "strided_index" : true },
],
Thanks man, now I see.
Tried this trick with my 560s. No go - driver crashes, pc restarts.