TL;DR: If you’re getting Code 10 errors with Mellanox ConnectX-4 Lx on Windows 10 with a consumer motherboard, update your BIOS. Everything else is a waste of time.
The Problem
Mellanox ConnectX-4 Lx shows Code 10 error in Device Manager on Windows 10 consumer motherboards. You’ll find dozens of “solutions” online. None of them actually work.
What Doesn’t Work (Stop Wasting Your Time)
I tried all of these. They don’t solve the root cause:
- Firmware update (
mlxup.exe) — Doesn’t fix Code 10 - Firmware reset (
mlxconfig reset) — Temporarily works, fails after reboot - SR-IOV disable (
mlxconfig set SRIOV_EN=0) — Still Code 10 - Shutdown script workaround (reset card on every shutdown) — Band-aid, not a fix
- Driver reinstall (latest or LTS) — Makes no difference
- Different PCIe slot — Doesn’t matter
- Registry tweaks — Pointless
- Disabling other devices — Irrelevant
These are workarounds at best. They don’t address the actual problem: your motherboard’s PCIe initialization logic is broken.
The Real Solution: BIOS Update
Update your motherboard BIOS to the latest version. That’s it.
Why This Works
Consumer motherboards (B660, B550, etc.) shipped with BIOS versions optimized for consumer hardware. Enterprise NICs like Mellanox weren’t tested. Manufacturers gradually fixed PCIe compatibility issues through BIOS updates over 2-3 years.
Example (MSI B660M Mortar):
- BIOS 1.10 (2021): Code 10 error
- BIOS v1H (2024): PCIe initialization improvements
- BIOS 1O (2026): Works perfectly
Result
After BIOS update:
- Both ports recognized
- 10Gbps link established
- No Code 10 error
- Stable across reboots
If BIOS Update Doesn’t Work
Give up on Mellanox. Buy a different NIC
My Setup
- Motherboard: MSI MAG B660M Mortar
- BIOS: 1.10 → 1O (2026-03-27)
- NIC: Mellanox ConnectX-4 Lx (OCP form factor)
- OS: Windows 10 22H2
- Result: 10Gbps working, no issues
Total troubleshooting: 8 hours. BIOS update: 10 minutes. Everything else: wasted time.
Conclusion
Don’t waste time with firmware resets, SR-IOV tweaks, or shutdown scripts. Update your BIOS first. If that doesn’t work, the problem is hardware incompatibility—buy a different NIC.
Tested: MSI MAG B660M Mortar, BIOS 1O, Windows 10 22H2
Date: 2026-04-19