I think your Sandy Bridge CPU might limit you to 2.0, even if your MB supports 3.0.

For reference, check the Expansion Options section here.

If your hardware does provide a way to set this manually, it would likely be somewhere in the (UEFI) bios configuration panel. On my Asus MB all the relevant settings are in Advanced -> Onboard Devices Configuration, but all I can configure is the amount of PCI lanes available. (And PCIe voltages in the overclocking section.)

Very good answer! In past month, I ask on windows forum to enabled it, but without success. Because my cpu is limited to PCIe 2.0. Thanks, I can stop to search how to do that!

Quoting: The_Aquabatsorry hijacking this post... my motherboard supports PCI gen 4 anyone saw any improvement when setting PCI GEN to 4?? because I didn't it's pointless.

No current consumer hardware really makes use of the kind of bandwidth PCIe 4.0 brings to the table. Even the fastest Nvidia GPUs do not come close to saturating a PCIe 3.0 16x bus, never mind 4.0.

So don't expect to see any effect on game performance right now.