Question: what is the difference between pci express x16 2.0 and 3.0?
Answer: PCIE 3.0 supports a max speed of 8.0 GT/s (Giga Transfers per second) where as PCIE 2.0 supports a max speed of 5.0 GT/s. The encoding used in PHY layer of PCIE 3.0 is 128B/130B encoding. But 8B/10B encoding is used in PCIE 2.0.