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Cykle
Journeyman III

6900XT does not work in PCIE4.0 x16 mode.

Hi there, got a bit of a headacke here.

Just got my 6900XT reference installed the other day and im having issues with the PCIE lanes.

Now i replaced it with a 6800XT MSI Trio X to the Reference 6900XT and got a EKWB block i wanna use on it but i dont dare install the block before i get this problem solved first if the card should be faulty.

My hardware is:
MSI B550 Unify-X
2x16Gb RipJaws (F4-3200C14-16GVR)
5800X
Corsair AX860I
256GB NVME PCIE 3.0
1TB NVME PCIE 3.0


Now my 6800XT was running flawlessly and without issues what so ever but when running the 6900XT i have to move the PCIE lanes from "Motherboard" to "CPU" in BIOS for the PC to boot up in PCIE4.0 but i can only get x8 and not x16.

Seems this problem was on the 5700XT too.
https://www.reddit.com/r/Amd/comments/cztzfi/disabling_pcie40_for_stable_boot_with_rx_5700_xt/

Any input on a fix would be apresiated.

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3 Replies
Cykle
Journeyman III

Update:

 

Seems i found the reason digging a bit deeper

https://forums.guru3d.com/threads/6800-xt-pci-e-4-0-and-the-strix-b550-e-solved-its-the-mobo.435452/

Limit of the B550 Chipset ffs!

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Have you read, https://www.msi.com/blog/m2-pcie-lane-configurations-for-b550-unify-unify-x

 

Ryzen 5 5600x, B550 aorus pro ac, Hyper 212 black, 2 x 16gb F4-3600c16dgtzn kit, Aorus gen4 1tb, Nitro+RX6900XT, RM850, Win.10 Pro., LC27G55T..

Thanks for the link.

 

Seems i can run in x16 mode when my 2 discs are populated in Slot 3+4.

 

Had one reboot failure out of 6 so time will tell if it's boot stable ☺️

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