why pcie has been developed?
PCIe provides lower latency and higher data transfer rates than parallel busses such as PCI and PCI-X. Every device that's connected to a motherboard with a PCIe link has its own dedicated point-to-point connection. ... PCIe can scale from one to 32 separate lanes; it is usually deployed with 1, 4, 8, 12, 16 or 32 lanes.