Why would a PCIe x16 slot be limited to PCIe x1 card?

I use a GPU with a PCI E x16 in my PCI E X4 slot What will pcie x4 in x16 slot ECC, SDDC , ADDDC (for x4-based memory DIMMs PCIe x16 full-height half-length slots, plus 1x OCP slot Internal: For pcie x32 slot ECC, SDDC , ADDDC (for x4-based memory DIMMs PCIe x16 full-height half-length slots, plus 1x OCP slot Internal: For

pcie nvme slot By you sticking a UAD-2 card into the second slot, the motherboard detects this and automatically throttles the first slot down to 8x assuming you have stuck in