24、 I / O device model (serial port / keyboard / disk / printer / bus / interrupt controller /dma and GPU)

One 、 Computer interface

CPU Work ： Take command , decoding , perform

1、 A serial port , Character input and output

2、 keyboard

Two 、 Bus 、 Interrupt controller and DMA

1、 Bus , special IO equipment

（1） Provide device registration and address forwarding to the device

（2）PCI Bus

        USB The bus is hanging on PCI On

2、 Interrupt controller

3、DMA,Direct Memory Access

（1）CPU Transfer data to the device , It's going to be inefficient

（2） Use a simple arithmetic unit to move data , After completion, notify by interruption CPU, Can greatly improve CPU efficiency

3、 ... and 、GPU And heterogeneous computing

1、PPU（NES Picture Processing Unit）

2、2D Realization 3D

（1） A three-dimensional polygon , It is also a polygon in the view plane

（2） whatever n Edge shape , Can be broken down into n-1 Triangles

3、 modern GPU： A general purpose computing device

A complete multicore multiprocessor

（1） Focus on a large number of parallel similar tasks

        for example ： Use OpenGL,CUDA

4、 Heterogeneous computing

（1） There are many cores in a chip （CPU、GPU、NPU、MPU）