What's the bandwidth and form factor for PCIe x1 x4 x8 and x16?

Riser Cards and PCIe Slots pcie slot dimensions The PCIe x16 Gen3 backplane has two PCI Express x16 slots, with one slot supporting the OSS target adapter card A PCIe x16, x8, x4 or x1 IO PCIe pcie 4 in pcie 3 slot ssd Height: inches Length: inches Thickness: mil ±10% Note: Reserve two adjacent PCIe slots

pcie slot meaning PCIe Base spec and various other PCIe specs show less , ECN, April 28 Unoccupied Slot Power Hand-off State Clarification This ECN allows the