Are UAD-2 cards supported on PCIe x4 or x16 slots?

Is a MacPro3,1 x16 slot PCIe or ? pcie slot x16 Risers with up to 4, x8 PCIe Slots + 2, x16 PCIe Slot is an expansion card that is used to extend a slot for an IO card in a fully loaded computer to make pcie 2 slot Have you ever thought if you can plug PCI Express cards into x16 lane slot? In this video

pcie 4 gpu in pcie 3 slot PCIe slots are used to connect graphics cards, sound cards, other interface cards and some