西安电子科技大学：《操作系统 Operating Systems》课程教学资源（PPT课件讲稿）Chapter 05 输入输出 Input/Output

Operating Systems Chapter 5: Input/Output 5,1 Principles of l/o hardwareⅣO硬件原理 5,2 Principles of lo software 10软件原理 4 5.3 10 software layers IO软件层次 H 5.4 Disks 盘 H 5.5 Clocks 时钟 56 Character- oriented terminals面向字符的终端 57 Graphical user interfaces图形用户界面 a 5.8 Network terminals 网络终端 耳59 Power management 电源管理 Gao Haichang, Software School, Xidian University 3

Operating Systems Gao Haichang , Software School, Xidian University 3 Chapter 5: Input/Output  5.1 Principles of I/O hardware I/O硬件原理  5.2 Principles of I/O software I/O软件原理  5.3 I/O software layers I/O软件层次  5.4 Disks 盘  5.5 Clocks 时钟  5.6 Character-oriented terminals 面向字符的终端  5.7 Graphical user interfaces 图形用户界面  5.8 Network terminals 网络终端  5.9 Power management 电源管理

Operating Systems oS control /o device g Main functions: u Send commands to the devices E Catch interrupts H Handle errors Provide an interface between the devices and the rest of the system that IS simple and easy to use e Device independence Gao Haichang, Software School, Xidian University

Operating Systems Gao Haichang , Software School, Xidian University 4 OS control I/O device  Main functions:  Send commands to the devices  Catch interrupts  Handle errors  Provide an interface between the devices and the rest of the system that is simple and easy to use  Device independence

Operating Systems Principles of 1/0 Hardware e Block device u Stores information in fixed -size blocks. each one with its own address I The essential property of a block device is that it is possible to read or write each block independently of all the other ones H Disks g Character device Delivers or accepts a stream of characters, without regard to any block structure w It is not addressable and does not have any seek operation t Printers. network interfaces. mouse Other device A cloc k Gao Haichang, Software School, Xidian University

Operating Systems Gao Haichang , Software School, Xidian University 5 Principles of I/O Hardware  Block device  Stores information in fixed-size blocks, each one with its own address.  The essential property of a block device is that it is possible to read or write each block independently of all the other ones.  Disks  Character device  Delivers or accepts a stream of characters, without regard to any block structure.  It is not addressable and does not have any seek operation.  Printers, network interfaces, mouse  Other device  clock

Operating Systems Principles of 1/0 Hardware Device Data rate Some typical Keyboard I 10 bytes/sec M 100 bytes/sec device network 56K modem 7 KB/sec and data base Telephone channel 8 KB/sec Dual ISDN lines 16 KB/sec rates Laser printer 100 KB/sec Scanner 400 KB/sec Classic Ethernet 1.25 MB/sec USB(Universal Serial Bus) 1.5 MB/sec Digital camcorder 4 MB/sec IDE disk 5 MB/sec 40X CD-ROM 6 MB/sec Fast Ethernet 12.5 MB/sec ISA bus 16.7 MB/sec EIDE(ATA-2)disk 16.7 MB/sec FireWire(IEEE 1394)50 MB/sec XGA Monitor 60 MB/sec SONET OC-12 network 78 MB/sec SCSI Ultra 2 disk 80 MB/sec Gigabit Ethernet 125 MB/sec Ultrium tape 320 MB/sec PCI bus 528 MB/s sec Sun Gigaplane XB backplane 20 GB/sec ao Haichang, software school, xidian Universl

Operating Systems Gao Haichang , Software School, Xidian University 6 Principles of I/O Hardware Some typical device, network, and data base rates

Operating Systems Device controllers elo devices have components A mechanical component device E electronic component g The electronic component is the device controller E may be able to handle multiple devices g Controller's tasks w Convert the serial bit stream into a block of bytes H Perform any error correction necessary H Copy it to main memory Gao Haichang, Software School, Xidian University

Operating Systems Gao Haichang , Software School, Xidian University 7 Device Controllers  I/O devices have components:  mechanical component （device）  electronic component  The electronic component is the device controller  may be able to handle multiple devices  Controller's tasks  Convert the serial bit stream into a block of bytes  Perform any error correction necessary  Copy it to main memory

Operating Systems Memory-Mapped 1/0 c Each controller has a few registers that are used for communication with cpu g Write into these registers os can command the device to deliver data accept data, switch itselfon or off, or otherwise perform some action G Read from these registers: OS can learn what the devices state is whether it is prepared to accept a new command, and so on c In addition to the control registers, many devices have a data buffer that the os can read and write(e.g video ram) c Q: How the CPU communicates with the control registers and the device data buffer? Gao Haichang, Software School, Xidian University

Operating Systems Gao Haichang , Software School, Xidian University 8 Memory-Mapped I/O  Each controller has a few registers that are used for communication with CPU.  Write into these registers: OS can command the device to deliver data, accept data, switch itself on or off, or otherwise perform some action.  Read from these registers: OS can learn what the device’s state is, whether it is prepared to accept a new command, and so on.  In addition to the control registers, many devices have a data buffer that the OS can read and write (e.g. video RAM).  Q: How the CPU communicates with the control registers and the device data buffer?

Operating Systems Memory-Mapped 1/0(2) Two address One address space Two address spaces OxFFFF Memory 1O ports 0 (a) (a)Separate 1o and memory space(IBM360) w Each control register is assigned an lo port number H Address spaces for memory and 1/O are different (b)Memory-mapped l/o(PDP-11) w Map all the control registers into the memory space H Each control register is assigned a unique memory address to which no memory is assigned (c) Hybrid(Pentium) H Memory-mapped 1/O data buffers, separate IO ports for the control registers

Operating Systems Gao Haichang , Software School, Xidian University 9 Memory-Mapped I/O (2)  (a) Separate I/O and memory space (IBM 360)  Each control register is assigned an I/O port number.  Address spaces for memory and I/O are different  (b) Memory-mapped I/O (PDP-11)  Map all the control registers into the memory space.  Each control register is assigned a unique memory address to which no memory is assigned.  (c) Hybrid (Pentium)  Memory-mapped I/O data buffers , separate I/O ports for the control registers

Operating Systems Memory-Mapped 1/0 Advantages G With memory-mapped 1O, a lo device driver can be written entirely in C. Otherwise, some assembly code is needed No special protection mechanism is needed to keep user processes from performing 10. G Every instructions that can reference memory can also reference control registers. Gao Haichang, Software School, Xidian University 10

Operating Systems Gao Haichang , Software School, Xidian University 10 Memory-Mapped I/O Advantages  With memory-mapped I/O, a I/O device driver can be written entirely in C. Otherwise, some assembly code is needed.  No special protection mechanism is needed to keep user processes from performing I/O.  Every instructions that can reference memory can also reference control registers

Operating Systems Memory-Mapped 1/0 Disadvantages e Most computers nowadays have some form of caching of memory words. Caching a device control register would be disastrous(blind to device ready) Selective disable caching adds extra complexity. G If there is only one address space then all memory modules and all lo devices must examine all memory references to see which ones to response to. Most modern computers have a dedicated high-speed memory bus, so O device have no way of seeing memory addresses as they go by on the memory bus. Gao Haichang, Software School, Xidian University

Operating Systems Gao Haichang , Software School, Xidian University 11 Memory-Mapped I/O Disadvantages  Most computers nowadays have some form of caching of memory words. Caching a device control register would be disastrous (blind to device ready). Selective disable caching adds extra complexity.  If there is only one address space, then all memory modules and all I/O devices must examine all memory references to see which ones to response to. Most modern computers have a dedicated high-speed memory bus, so I/O device have no way of seeing memory addresses as they go by on the memory bus

Operating Systems Memory-Mapped 1/0 Disadvantages CPU reads and writes of memory go over this high-bandwidth bus CPU Memory CPU Memory O All addresses( memory This memory port is to allow l/o devices and / o)go here Bu access to memory (a)a single-bus architecture (b )a dual-bus memory architecture Gao Haichang, Software School, Xidian University 12

Operating Systems Gao Haichang , Software School, Xidian University 12 Memory-Mapped I/O Disadvantages (a) A single-bus architecture (b) A dual-bus memory architecture