MoBa PCI lanes
MoBa PCI lanes
Your setup allows you to allocate full 16x lanes to one GPU and use the other for partial utilization.
Choose the last PCIe port connected at x4. Using the second x16 port isn't possible.
The slot is connected in a different way than the second X16 slot (which passes through the chipset), and you don’t have to adjust any settings in BIOS to make this change.