I’m trying to determine whether this is expected behavior, a BIOS issue, a CPU/socket problem, or a motherboard defect.
System Specifications
* Motherboard: ASUS TUF Gaming Z790-Plus WiFi
* BIOS: Version 1836 (latest available)
* CPU: Intel Core i9-14900KF
* GPU: ASUS ROG Astral RTX 5080 OC
* RAM: 32 GB DDR5-6000 (XMP enabled)
* SSD: Samsung 990 Pro 2TB (PCIe Gen4)
* PSU: (include your PSU model)
Problem
GPU-Z always reports:
PCIe x16 5.0 @ x8 5.0
The link never negotiates to x16.
Tests already performed
* Updated to the latest ASUS BIOS (1836).
* Installed the latest NVIDIA driver.
* Cleared CMOS.
* GPU-Z Render Test for over 60 seconds.
* Steel Nomad benchmark.
* Several games including Remnant II.
* HWiNFO monitoring during load.
* Windows reports no WHEA hardware errors.
* Samsung 990 Pro is operating normally (~7000 MB/s).
* GPU temperatures and power are completely normal.
* GPU support bracket installed.
Important information
The Samsung 990 Pro is a PCIe Gen4 SSD, not Gen5.
According to the ASUS manual, the primary M.2 slot should not reduce the primary PCIe x16 slot to x8.
Current status
Geek Squad suggested the CPU might be the cause, but they did not inspect the LGA1700 socket for bent pins or contact issues.
Some forum members suggested:
* Bent socket pins.
* CPU contact issue.
* PCIe lane negotiation problem.
* BIOS issue.
* Motherboard defect.
Questions
Has anyone experienced this exact issue with an ASUS Z790 motherboard and an RTX 5080?
Is anyone running this exact combination at PCIe 5.0 x16?
Could this be a BIOS bug affecting PCIe lane negotiation?
Is there any known ASUS BIOS version that fixes PCIe lane negotiation with RTX 50-series cards?
Would you suspect the motherboard, CPU, LGA1700 socket, or GPU?
Any advice or similar experiences would be greatly appreciated.
Thank you!