The x16 slot of your motherboard runs at PCIe 3.0 if you have a 3rd generation Intel Core processor (Ivy Bridge), or PCIe 2.0 if you have a 2nd generation Intel Core processor (Sandy Bridge).
The x16 slot of your motherboard runs at PCIe 3.0 if you have a 3rd generation Intel Core processor (Ivy Bridge), or PCIe 2.0 if you have a 2nd generation Intel Core processor (Sandy Bridge).