第2章硬件的环境 No Slide Title.ppt

实用操作系统概念 内容框架 概述 体系结构 进程管理 内存管理 文件管理 外设管理 内容 Ch2: 计算机体系结构 Ch3: 操作系统体系结构 Ch2：体系结构 Modern computer system structure 中断机制 CPU I/O Structure Storage Structure Hardware Protection General System Architecture Modern computer system structure I/O devices and the CPU can execute concurrently. Each device controller is in charge of a particular device type. Each device controller has a local buffer. CPU moves data from/to main memory to/from local buffers I/O is from the device to local buffer of controller. Device controller informs CPU that it has finished its operation by causing an interrupt. 中断机制 An operating system is interrupt driven Interrupts transfers control to the interrupt service routine generally, through the interrupt vector, which contains the addresses of all the service routines. Interrupt architecture must save the address of the interrupted instruction. Incoming interrupts are disabled while another interrupt is being processed to prevent a lost interrupt.. 中断机制 The operating system preserves the state of the CPU by storing registers and the program counter. Determines which type of interrupt has occurred: polling vectored interrupt system Separate segments of code determine what action should be taken for each type of interrupt I/O Structure Two I/O methods Two I/O methods Synchronous After I/O starts, control returns to user program only upon I/O completion. wait instruction idles the CPU until the next interrupt wait loop (contention for memory access). At most one I/O request is outstanding at a time, no simultaneous I/O processing. Two I/O methods Asynchronous After I/O starts, control returns to user program without waiting for I/O completion. System call – request to the operating system to allow user to wait for I/O completion. Device-status table contains entry for each I/O device indicating its type, address, and state. Operating system indexes into I/O device table to determine device status and to