PCIe generation - speed mismatch

What is PCIE-GEN-MISMATCH?

PCIE-GEN-MISMATCH shows up as a medium-severity motherboard fault. GPU or NVMe SSD running on PCIe 3.0 instead of PCIe 4.0/5.0, performance is significantly reduced. Reports of PCIe generation - speed mismatch usually describe a sudden crash, brief unresponsiveness, or a stop-code screen appearing out of nowhere. Work through the steps below in order.

Common Causes

• The CPU or board does not support the higher generation PCIe
• GPU in secondary slot which is limited to PCIe 3.0 x4
• Incorrect PCIe settings in BIOS (Gen 1/2/3 instead of Auto)

Step-by-Step Fix Guide

• 1
  Set PCIe slot to Auto or Gen4 in BIOS

  Most reports of PCIE-GEN-MISMATCH clear up after Set PCIe slot to Auto or Gen4 in BIOS, so it's worth trying before anything more involved.

• 2
  Move the GPU to the primary PCIe x16 slot

  When the first step isn't enough, the later steps handle the edge cases tied to mobo instability.

• 3
  Verify GPU speed with GPU-Z Bus Interface tab

  For lingering PCIE-GEN-MISMATCH cases, "Verify GPU speed with GPU-Z Bus Interface tab" is worth running through.

Commands & Diagnostics

Frequently Asked Questions