Asus ROG Strix B650-A M.2 Running on 2 lanes. Tried different drives still persists

[Will3131]

I recently built a new system, 7800X3D, Asus ROG Strix B650-A. I have a WD SN850X and a Crucial P5 Plus. Both are Gen4 drives. When I place them in the top M.2 slot, they both run at Gen 4 2 lanes, not GEN 4 4 lanes. There is no limitation to that slot with this motherboard. 

Anyone else have this issue, and know how to fix? They both work as GEN 4 4lanes in the other slots but not the top one. It's a brand new system only 24 hours old. 

[Pandur]

Since you have the same issue with two different ssds, this sadly points to a hardware issue.

Inspect the M.2 for debris, bits of a sticker, or something like that. If you have a bottle of compressed air use that to clean out the socket.

Otherwise I would suspect damaged pins in the M.2 or CPU socket, or a defective CPU. If you are not very careful you can easily damage a pin or two in the CPU socket during installation. Hit the correct pin(s) and this will happen.

Since both M.2_1 and M.2_2 are connected to the CPU, the performance and functionality should be identical when using PCIE 4.0 drives.

[akadeepakjadhav]

1. Check BIOS Settings:

PCIe Lane Allocation: Ensure the top M.2 slot is configured to run at Gen 4 4 lanes in the BIOS.
CPU PCIe Configuration: Verify that the CPU is correctly configured to allocate enough PCIe lanes to the motherboard.
M.2 Slot Configuration: Double-check if there's a specific setting for the top M.2 slot that might be limiting its bandwidth.
2. Update BIOS and Drivers:

BIOS Update: A newer BIOS version might have bug fixes or improvements related to M.2 slot performance.
Driver Updates: Ensure that the latest chipset and storage controller drivers are installed.
3. Test with Other Cables and Drives:

Different Cables: Try using different M.2 cables to rule out any cable-related issues.
Other Drives: Test with a different Gen 4 NVMe drive to see if the problem persists.
4. Check for Physical Obstructions:

Heatsink Interference: Ensure that the M.2 drive's heatsink isn't blocking PCIe lanes or interfering with the slot.
Cable Routing: Make sure cables aren't obstructing the M.2 slot or causing physical pressure.
5. Verify Motherboard Compatibility:

Check Manual: Refer to the motherboard's manual to confirm if there are any specific limitations or requirements for the top M.2 slot.
Contact ASUS Support: Reach out to ASUS support for further assistance or troubleshooting advice.
6. Consider Hardware Compatibility:

CPU Compatibility: Ensure that the CPU is compatible with Gen 4 NVMe drives and can allocate enough PCIe lanes.
Power Supply: Verify that the power supply can provide sufficient power to the motherboard and NVMe drives.
7. Check for Overclocking or Tweaking:

Reset BIOS: If you've overclocked or tweaked any settings, try resetting the BIOS to default values and see if the issue resolves.

[Will3131 · Accepted solution]

Hello, 

Thanks for the assistance. It ended up being the motherboard. There were no damaged pins or any visible damage to the motherboard it was brand new out of the box, and I've been building PC's for well over 20 years. This motherboard just seemed to have a defect from the factory. Ended up switching it out with a brand-new Asus ROG Strix B650E-F Gaming Wifi. No issues with this one.