Unknown. Help us by suggesting a value. (Asus P10S WS)
PCIe slots allow you to connect graphics cards, SSDs, and other components to the motherboard. The number after the 'x' represents the number of lanes, with more lanes supporting higher data transfer rates. PCI Express 2.0 has a transfer rate of 5 GT/s, providing 500 MB/s per lane.
PCIe 2.0 x16 slots: is this important to you?