I'm troubleshooting an ASUS TUF Gaming Z790-Plus WiFi system with an Intel Core i9-14900KF, ASUS ROG Astral RTX 5080 OC, 32GB of DDR5-6000, and a Samsung 990 Pro 2TB PCIe 4.0 SSD. BIOS 1836 and the latest NVIDIA drivers are installed. GPU-Z consistently reports the graphics card as PCIe 5.0 x8, even during the Render Test, Steel Nomad, and several games. The link never changes to x16 under load. I have already cleared CMOS, confirmed the card is installed directly in the primary PCIe x16 slot, had it reseated, and verified that temperatures, power, storage performance, and Windows hardware-error reporting all look normal. There is no riser cable. The motherboard manual indicates that the primary M.2 slot should not reduce the main graphics slot to x8, and the SSD is only PCIe 4.0. Could this be caused by the CPU, LGA1700 socket pins or contact pressure, motherboard circuitry, firmware, or the graphics card itself? Has anyone run this combination at PCIe 5.0 x16, or found a BIOS or hardware fix for similar behavior?
4 Answers
Even if x8 is the final result, PCIe 5.0 x8 has roughly the bandwidth of PCIe 4.0 x16, so the practical gaming performance loss should usually be very small. That does not prove the configuration is correct, though. If you want to identify the cause, inspect the socket and CPU contact first, then test with another GPU or board and check ASUS firmware notes for any PCIe compatibility fixes.
First, make sure the link speed is being checked while the GPU is under sustained load. PCIe can downshift when idle, so GPU-Z may show a lower active link state outside a render test. Since you’ve already tested with GPU-Z, benchmarks, and games and it remains at x8, this sounds like a real link-width limitation rather than normal idle behavior.
A CPU or motherboard contact problem is plausible. On this platform, damaged or poorly contacting socket pins can affect PCIe lanes, so inspect the LGA1700 socket carefully under good lighting and reseat the CPU if necessary. If the socket looks fine, testing another graphics card or motherboard would help isolate the fault.
Try temporarily moving the Samsung 990 Pro to a lower M.2 slot and retest. The manual suggests the top slot should not steal lanes from the main x16 slot, but changing the slot is an easy way to rule out lane-sharing or firmware behavior. Also check the BIOS PCIe configuration and set the primary slot to Auto or Gen 5 rather than forcing an unusual mode.
The SSD is a Gen4 drive, so it should not normally consume the graphics card’s lanes on this board. Still, moving it is a worthwhile diagnostic step before assuming the motherboard or CPU is defective.
That was my concern as well. I checked during the GPU-Z Render Test, Steel Nomad, and gaming sessions, but it stayed at PCIe 5.0 x8 throughout.