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ROG Crosshair VIII Extreme DIMM.2 Bandwidth

Level 7
Hi. I just purchased the CH VIII Extreme and the DIMM.2 was one of the factors that attracted me. I'm running a 5950x, 3090 Kingpin, 32GB RAM, WD SN750 Black 500GB PCIE 3 M.2 in M.2-1 slot on board as a boot drive and 2 WD SN850 Black 1TB PCIE 4 M.2's on the DIMM.2 as game drives. I prefer not to run them on the MB M.2 slots 2 and 3 because I would drop to 3090 to 8x interface. In CrystalDiskMArk the SN850's should get about 7000 seq reads and did in my previous Dark Hero board. In the DIMM.2 one of them gets just over 6000 and the other only 3000. Is there a setting in the UEFi that I'm missing or is this just a bandwidth limitation? If I run them in raid 0 on the DIMM.2 I get just over 5000 and was getting about 13,000 in raid 0 on the Dark Hero. Thanks!

Level 7
This is happening to me also. Using Samsung Magician I can see under drive details that' it's running at x2 lanes instead of x4.

My situation is worst, 1TB ssd crash my system when using this dimm.2 slot. It booted twice but later crashed the whole windows.
Is there any driver or setting in bios which I'm missing to enable it.
Formatted disk with gpt and running windows 11 pro.

BIOS update fixed my issue.