If your motherboard, CPU and graphics cards all support PCIe 3.0 then shouldn't everything run at PCIe 3.0 speeds? The answer is no, by default your motherboard and graphics cards will only run at PCIe 2.0 speeds which significantly hinders system and gaming performance. You have to Force Enable PCIe 3.0. By enabling PCIe 3.0 you will see a frame-rate increase of anywhere from 30-100 frames per second in-game. Lag and choppy game-play will be a thing of the past. When running the Unigen Heaven 4.0 Benchmark on absolute max settings I was hitting an average frame-rate of about 80fps, after enabling PCIe 3.0 support my average FPS jumped to a whopping 123fps. In the Unigen Heaven Benchmark this kind of frame-rate jump is monstrous. Check out the tutorial steps below on specifically how to force enable PCIe gen3 on your system.
Here's the tutorial: http://www.trickmasterpc.com/force-enable-gen3-pcie-3.html