check the BIOS if 3.0 is enabled, sometimes it shows as 2.0 but when the gpu starts to perform with load with will go to 3.0.
kind of a backward compatibility thing. put some load on the GPU and check.
when the card is idle it runs at min setting thats why
PCI-E 3.0 is only available on Core i5 and i7 3xxx CPUs. Sandy Bridge CPUs, and Ivy Bridge based i3s, Pentiums and Celerons don't have PCI-E 3.0 support. The PCIe slot both support 3.0 and 2.0 PCIe X16.