I/O interface chips: most chips are integrated circuits, which can input different parameters and commands through the CPU, and control related I/O circuits and some simple peripherals for related operations. Common interface chips include interrupt controller, parallel interface, counter and DMA controller. I/O interface control card: the control card is mainly composed of multiple integrated circuits according to certain logic, or directly on the same motherboard as the CPU, or a plug-in inserted in the system bus slot; There are differences between the classification of wire harness machining interface: speed mismatch: I/O device operating speed is much slower than CPU, and due to different types of speed differences are also great; Timing mismatch: each I/O device has its own timing control circuit, which transmits data at its own speed and cannot be consistent with the timing of the CPU.