3DMark is a program with a set of several 3D benchmarks. Fire Strike benchmark measures DirectX 11 performance and is targeted to high-end gaming computers. Sky Diver also measures DirectX 11 performance, and is aimed on average computers. The Cloud Gate benchmark measures DirectX 10 performance. The Ice Storm measures DirectX 9 performance and is targeted to entry-level computers, so we did not include it on our comparison.
Keep in mind that we used a GeForce GTX 980 Ti video card on all tests.
We ran every benchmark three times, and each number in the graphs is the arithmetical mean between the obtained scores.
On Fire Strike, the performance was the same on all the configurations.
On Sky Diver, there was no difference between the PCI Express 3.0 x16 and PCI Express 2.0 x16 benchmarks. On the other hand, on the test using PCI Express 3.0 x4, the performance was 5.5% below the first test.
On the Cloud Gate benchmark there was also no difference between PCI Express 2.0 and 3.0, but the test using PCI Express 3.0 x4 leaded to a 7.9% lower performance.