B450 Tomahawk – GPU drops to PCIe x8 when M.2 is installed (BIOS 7C02v1J8 Beta)

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pablomoradooliveir15ba02dc

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Hello MSI Support,

I'm reaching out about a reproducible issue I've found with my B450 Tomahawk.

Setup:
- Motherboard: MSI B450 Tomahawk
- CPU: AMD Ryzen 5 5600
- GPU: AMD RX 6700 XT
- BIOS version: 7C02v1J8 (Beta)

Issue:
When an NVMe SSD is installed in the M.2 slot, the primary PCIe x16 slot (PCI_E1) drops to x8 speed under load, as reported by GPU-Z. Removing the NVMe restores the slot to x16. The board's specification states that the M.2 slot uses separate CPU lanes and should only disable SATA5/6 ports, with no mention of any impact on PCI_E1 bandwidth.

I've confirmed the behaviour on both Windows and a Linux live environment, ruling out any OS or driver cause.

Could you let me know if there is a stable or upcoming BIOS version that addresses this? I'm currently on a beta build and would prefer to move to a stable release if a fix is available.

Thank you for your time.
 
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pablomoradooliveir15ba02dc said:
Hello MSI Support,

I'm reaching out about a reproducible issue I've found with my B450 Tomahawk.

Setup:
- Motherboard: MSI B450 Tomahawk
- CPU: AMD Ryzen 5 5600
- GPU: AMD RX 6700 XT
- BIOS version: 7C02v1J8 (Beta)

Issue:
When an NVMe SSD is installed in the M.2 slot, the primary PCIe x16 slot (PCI_E1) drops to x8 speed under load, as reported by GPU-Z. Removing the NVMe restores the slot to x16. The board's specification states that the M.2 slot uses separate CPU lanes and should only disable SATA5/6 ports, with no mention of any impact on PCI_E1 bandwidth.

I've confirmed the behaviour on both Windows and a Linux live environment, ruling out any OS or driver cause.

Could you let me know if there is a stable or upcoming BIOS version that addresses this? I'm currently on a beta build and would prefer to move to a stable release if a fix is available.

Thank you for your time.
Ultimo post : 2026-05-17 09:23
Click to expand...

First, try updating your SSD firmware.
I also recommend installing the official BIOS version
instead of the beta version.
Start by updating to the latest official BIOS.
If the speed drops from 16x to 8x, uninstall your graphics card driver
and reinstall it—that should resolve the issue.



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Thanks Tourica, I tried downgrading the BIOS to 7C02v1I which was from 2022 (the latest beta version is from 2025), same behaviour. I downloaded Samsung Magician and updated the M.2 firmware. Lastly, I booted into safe mode to run DDU to uninstall GPU drivers and reinstalled them from the latest version. GPU-Z is still showing x8 3.0 as active speed on the PCI_E1 WHEN I connect the M.2 into the M.2 slot...
 
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