It is usually said that the computer has address, data, control three buses, because the bus needs to drive the load, the CPU is a large-scale integrated circuit, does not have the power drive ability, the role of the bus driver is to provide power drive, the second reason is that the CPU bus is often a time-sharing multiplexed bus, that is, at different times, the signal function on the pin is different. A latch is needed to store and separate signals, and the bus driver acts as a latch.