Crosshair VIII Extreme with DIMM.2 and M2_1 not getting x16 for GPU

[PvtBeavis]

I have the following:
Crosshair VIII Extreme
5800X3D
2 Samsung 990 Pros 2TB in Dimm.2
1 Sabarent Rocket 1TB
6800XT Saphire Pulse in PCIEX16_1
Mellanox PCIx Card in PCIEX16_2

All drives are detected. However, the graphics card is only showing using x8 and not x16. Any suggestions on best optimal layout for this? I would like to get x16. I may also take out the Mellanox card(only using for fiber to get 10G from NAS), may switch out to RJ45 in order to use 10G on motherboard. Thanks!

[Murph_9000]

It's the Mellanox that's taking half your GPU lanes. There's only one x16 bus on the CPU, so it's either x16/0 or x8/x8 for the 2 PCIEX16 slots. M.2_2 and M.2_3 also share the CPU's single x16, similarly reducing the top slot to x8. M.2_1 uses the separate x4 storage lanes from the CPU. DIMM.2 and PCIEX1 are through the chipset. See page xiii of the manual for the shared lanes and possible configurations.

You can happily use PCIEX16_1, M.2_1, and both DIMM.2 slots simultaneously; while getting the full x16 to the GPU.

[PvtBeavis]

Thank you! I had a feeling that was it.