PCI Express X1 to X16 Low Profile Slot Extension Adapter

PCI-E x16 slots can run other cards As for the board ,you need a motherboard with intel x38,x48 or p45 chipset, but I'm not sure if

AMD B550 Ultra Durable Motherboard with Digital VRM Solution, PCIe x16 Slot 1x PCIe ® Slot 2 2280 • NVMe PCIe x4 and SATA Mode

pcie 4 gpu in pcie 3 slot Or will they only work on a PCI-Ex1 slot? Reason being I am looking at buying an MSI 990FXA-GD80 MoBo I want to use the second card slot

pcie slot width Any PCI Express card of a smaller size will fit into a larger slot So an x1 card will fit in an x8 slot Please see the Wikipedia article