I've now started mining with ethminer, however, even though it is correctly using my GPU (its usage is constantly at 100%), the program is also maxing out two of my four cores, to the point where their temperature is higher than the GPU's, I thought it was supposed not to use it, expecially because considering that using the CPU for mining is basically a waste of energy.
By the way, my graphics card is an NVIDIA gtx970 and my processor is an i7-4790k.