Unknown. Help us by suggesting a value. (Asus B75M-Plus)
PCIe slots enable you to connect various components to your motherboard, for example, graphics cards, RAID cards, SSDs. The number of data-transmission lanes (specified by the number following 'x') determines the data transfer rate. A PCIe x4 slot has 4 lanes, with a speed of 4 bits per cycle.
PCIe x4 slots: is this important to you?