I bought this GPU off Ebay used a couple of years ago. At first I had it in an Asus Maximus XI Hero WiFi w/9900K. I could never get x16 to work in PCIe x16 3.0 mode. It will only do x8. I then put it in an ASRock X99 Extreme4 3.1 w/Xeon E5 2699 V4. Same issue. I just tried it in a new ASRock Z690 Steel Legend WiFi w/i7 12700K and have the same issue. The GPU works fine otherwise. Could it be a hardware issue?