This problem has plagued me for months and I have tried everything to solve it. I just stumbled on something which has solved the problem outright for me. In my motherboard bios, I changed the PCIE setting to Gen 2 from Auto. I happened to read in the small print that my motherboard won't support Gen 3 unless I have an APU installed which I don't. Since doing this, my PC hasn't missed a beat playing even the most demanding games.