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计算机专业外语翻译
chapter 1 Principles Of Computer OrganizationCHAPTER 1 PRINCIPLES OF COMPUTER ORGANIZATIONINTRODUTIONThe generic computer contains input devices, a computational unit, and output devices. The computational unit is the computer's heart, and usually consists of a central processing unit (CPU), a memory, an input/output (I/O) interface and other important components. To get a better understanding of computer organizaion, a brief overview of the computers organization is given in the flowing. 一般计算机包含输入设备，计算单元，和输出设备。计算单 元是计算机的心脏，通常包括一个中央处理单元（ CPU ） ，存 储器，输入/输出（ I / O ）接口和其他重要的组成部分。为了 更好地了解计算机组成，下面简要概述了计算机的组成。1.1 COMPUTER HARDWAREWe build computer to solve problems. Early computer solved mathematical and engineering problems, and later computerschapter 1 Principles Of Computer Organizationemphasized information processing for business applications. Today, computers also control machines as diverse as automobile engines, robots, and microwave ovens. A computer system solves a problem from any of these domains by accepting input, processing it, and producing output. 我们创造计算机是为了解决问题。早期的计算机解决数学和 工程问题，后来的计算机主要用于商业应用的信息处理方面。今 天，电脑还可以控制机器设备，如：汽车发动机，机器人，微波 炉。计算机系统通过接受输入，处理，并产生输出来解决这些领 域中的相关问题。Fig.1.1 the three activities of a computer systemComputer systems consist of hardware and software. Hardware is the physical part of the system. Once designed, hardware is difficult and expensive to change. Software is the set of programs that instruct the hardware and is easier to modify than hardware. Computers are valuable because they are general-purpose machines that can solve many different kinds of problems, as opposed to special-purpose machines that can each solve only one kind of problem[1].Different problems can be solved with the same hardware by supplying the system with a different set of instructions, that is, with different software. 计算机系统包括硬件和软件。硬件是计算机系统的物理部 分，一旦设计，改变硬件是一件很难而且昂贵的事情。软件是指 示硬件工作的一套程序，与改变硬件相比更容易修改。由于计算 机是能够解决多种不同类型问题的通用机器，而不是仅解决某一 [1] 类问题的专用机器，它们具有（重要）价值 。通过给系统提供chapter 1 Principles Of Computer Organization不同的指令集，也就是说，不同的软件，可以使相同的硬件解决 不同的问题。 Every computer has four basic hardware components.? ? ? ? Input devices. Output devices. Main memory. Central processing unit (CPU).每台计算机都由四个基本硬件组件。 ? 输入设备. ? 输出设备. ? 主存储器. ? 中央处理单元(CPU). Fig.1.2 shows these components in a block diagram. The lines between the blocks represent the flow of information flows from one component to another on the bus, which is simply a group of wires connecting the components. Processing occurs in the CPU and main memory. The organization in Fig.1.2, with the components connected to each other by the bus, is common. However, other configurations are possible as well. 图 1.2 在结构图中显示了这些组件。模块之间的连线代表信 息流通过总线从一个组件流入到另一个组件的流向，总线只不过 是连接组成部分的一组电线。信息处理发生在 CPU 和主存储器。 从组织结构图 1.2 ， 组件之间通常是通过总线彼此相连的。 然而， 其他配置也是可能的。 Computer hardware is often classified by its relative physical size. ? S ? Mchapter 1 Principles Of Computer Organization ?Large mainframe.Fig.1.2 Block diagram of the four components of a computer system计算机硬件通常是按相对物理尺寸来划分。 ? 微型计算机; ? 中等小型机; ? 大型主机. Just the CPU of a mainframe often occupies an entire cabinet. Its input/output (I/O) devices and memory might fill an entire room. Microcomputers can be small enough to fit on a desk or in a briefcase. As technology advances, the amount of processing previously possible only on large machines becomes possible on smaller machines. Microcomputers now can do much of the work that only minicomputers or mainframes could do in the past. 大型主机的 CPU 主机往往占据整个橱柜。 它的输入/输出 （I / O ）设备和内存也可能填满整个房间。微型计算机可以足够小， 适合于办公桌或公文包里。随着技术的进步，以前只能在大型机 上的处理数据量现在在小型机上变为可能。微机现在可以做许多 以前只有小型机或大型机可以做的工作。 The classification just described is based on physical size as opposed to storage size. A computer system user is generally more concerned with storage size, because that is amore direct indication of the amount of useful work that the hardware can perform[2]. 刚才所描述的分类是基于物理尺寸，而不是存储容量。计算 机用户通常更关心存储容量的大小，因为它是硬件能够执行的有chapter 1 Principles Of Computer Organization用工作量的更直接的指示。 Speed of computation is another characteristic that is important to the user. Generally speaking, users want a fast CPU and large amounts of storage, but a physically small machine for the I/O devices and main memory. 计算速度对于用户来说是计算机的另一个特征。一般来说， 用户除了需要一个小体积机器的 I / O 设备和主存储器外，还需 要一个快速的 CPU 和大量的存储空间。 When computer scientists study problems, therefore, they are concerned with space and time-the space necessary inside a computer system to store a problem and the time required to solve it. They commonly use the metric prefixes of TABLE 1.1 to express large or small quantities of space or time. 因此，当计算机科学家研究问题的时候，他们所关心的是空 间和时间，也就是在计算机系统里面存储问题的必要的空间内和 解决问题所需的时间。他们通常使用表 1.1 的公制前缀来表示， 空间或时间的大小量。Table 1.1 Prefixes for powers of 10 Multiple 10 10 10 109 6Prefix gigamegakilomillimicronano-Abbrev G M K m u n103-3 -610-9Example Suppose it takes 4.5 microseconds, also written 4.5 us, to transfer some information across the bus from one component to another. (a) How many seconds are required for the transfer? (b) How many transfers can take place during one minute?chapter 1 Principles Of Computer Organization例如：假设要通过总线从一个组件传递一些信息到另一个组 件需要 4.5 微秒， 也可以写成 4.5us。 （ a ） 传递需要多少秒？ （b）在一分钟内可以传递多少？ (a) A time of 4.5ps is 4.5 X 10-6 from TABLE 1.1 or 0. 000 004 5 s. (b) Because there are 60 seconds in one minute, the number of times the transfer can occur is (60 s)/(0. 000 004 5 s/transfer) or 13 300 000 transfers. Note that since the original value was given with two significant figures, the result should not be given to more than two or three significant figures. （a）4.5ps 从表 1.1 是 4.5 ×10-6 或 0 .000 004 5 秒（ b ） 由于一分钟有 60 秒， 可能发生的传递次数是 （ 60s） / （ 0 .000 004 5 秒/传递）或 13 300 000 传递。请注意，由于原值是带有 两个有效数字，其结果不应该考虑到多于两个或三个有效数字。 Table1.1 shows that in the metric system the prefix kilo-is 1000 and mega- is 1000000. But in computer science, a kilo-is 210 or 1024. The different between 1000 and 1024 is less than 3%, so you can think of a computer science kilo- as being about 1000 even though it is a little more. The same applies' to mega- and giga-, as in Table1.2. This time, the approximation is a little worse, but for mega-it is still within 5%. Table1.1 表明，在公制系统前缀中，前缀 kilo 是 1000 和前 10 缀 mega 是特大 1000000 。但是，在计算机科学中，一千，是 2 或 1024 。1000 和 1024 之间的差距小于 3 ％ ，所以你可以认为 计算机科学 kilo 约为 1000 尽管它稍微多一点。在 Table1.2 里 mega（兆）和千兆同样也适用。这时这一次，两者的近似值差距 稍微大一些，但对于兆来说它仍然在 5 ％以内。Table 1.2 Computer science values of the large prefixeschapter 1 Principles Of Computer Organization Prefix gigamegakiloComputer science value 230 =1 073 741 824 220 =1 048 576 210 = 1 024Keywords and Abbreviations:computer information processing hardware software program microcomputer mainframe 计算机 信息处理 硬件 软件 程序 微型计算机 主机， 特大型 input device output device main memory bus instruction minicomputer general-purpose machine 中央处理器 专用计算机 输入设备 输出设备 主存储器 总线 指令 小型计算机 通用计算机central processing unit (CPU) pecial-purpose machineNotes：[1]Computers are valuable because they are general-purpose machines that can solve many different kinds of problems, as opposed to special-purpose machines that can each solve only one kind of problem. 由于计算机是能够解决多种不同类型问题的通用机器，而不 是仅解决某一类问题的专用机器，它们具有（重要）价值。 [2] A computer system user is generally more concerned with storagechapter 1 Principles Of Computer Organizationsize, because that is amore direct indication of the amount of useful work that the hardware can perform. 计算机用户通常更关心存储容量的大小，因为它是硬件能够 执行的有用工作量的更直接的指示。1.2 PROCESSORA processor is a functional unit that interprets and carries out instructions. Every processor comes with a unique set of operations such as ADD, STORE, or LOAD that represent the processor's instruction set[1].Computer designers are fond of calling their computers machines, so the instruction set is sometimes referred to as machine instructions and the binary language in which they are written is called machine language! You shouldn't confuse the processor's instruction set with the instructions found in high-level programming languages, such as BASIC or Pascal.处理器是解释并执行指令的功能部件。 每个处理器都有一 个诸如 ADD、STORE 或 LOAD 之类的操作集，这个操作集 就是该处理器的指令系统。 计算机系统设计者习惯将计算机称 为机器， 所以该指令系统有时也称作机器指令系统， 而书写指 令的二进制语言叫做机器语言。 注意， 不要将处理器的指令系 统与 BASIC 或 PASCAL 这样的高级程序设计语言中的指令系 统相混淆。 An instruction is made up of operations that specify the function to be performed and operands that represent the data to be operated on. For example, if an instruction is to perform the operation of adding two numbers, it must know (1) what the two numbers are and (2) where the two numbers are. When the numbers are stored in the computer'schapter 1 Principles Of Computer Organizationmemory, they have their addresses to indicate where they are. So if an operand refers to data in the computer's memory it is called an address. The processor's job is to retrieve instructions and operands from memory and to perform each operation[2]. Having done that, it signals memory to send it the next instruction..指令由操作码和操作数组成， 其中操作码指明要完成的操 作功能，而操作数则表示所处理的数据。例如，一条指令要完 成两数相加的操作，它就必须知道：（1）这两个数是什么？ （2）这两个数在哪儿？当参与操作的数存储在计算机内存中 时，应有指明该操作数存放的内存地址，所以，如果操作数表 示的是计算机内存中的数据， 则该操作数叫做地址。 处理器的 工作就是从存储器中获得指令和操作数， 并执行每个操作。 处 理器完成这些工作后就通知存储器送来下一条指令。 This step-by-step operation is repeated over and over again at awesome Speed. A timer called a clock releases precisely timed electrical signals that provide a regular pulse for the processor's work. The term that is used to measure the computer's speed is borrowed from the domain of electrical engineering and is called a megahertz (MHz), which means million cycles per second. For example, in an 8-MHz processor, the computer's clock ticks 8 million times to every 1 second tick of an ordinary clock. 处理器以惊人的速度一遍又一遍地重复以上一步步的操 作。 一个称作时钟的计时器准确地发出定时电信号， 该信号为 处理器工作提供有规律的脉冲。 测量计算机速度的术语是从电 工领域借用来的，称作兆赫（MHz），兆赫意指每秒百万个周 期。例如，普通时钟每秒滴答一次，而在8MHz的处理器中， 计算机的时钟则滴答了800万次。 A processor is composed of two functional units a control unit and an arithmetic/logic unit--and a set of special workspaces calledchapter 1 Principles Of Computer Organizationregisters.处理器由两个功能部件（控制部件和算术/逻辑部件）和 一组称作寄存器的特殊工作空间组成。 1. The Control Unit The control unit is the functional unit that is responsible for supervising the operation of the entire computer system. In some ways, it is analogous to a telephone switch-board with intelligence because it makes the connections between various functional units of the computer system and calls into operation each unit that is required by the program currently in operation. I 控制部件 控制部件是负责监控整个计算机系统操作的功能部件。 从 某些方面看， 它类似于智能电话交换机， 因为它将计算机系统 的各功能部件连接起来， 并按正在执行中的程序的需要， 控制 每个部件完成操作。 The control unit fetches instructions from memory and determines their types or decodes them. It then breaks each instruction into a series of simple small steps or actions. By doing this, it controls the step-by-step operation of the entire computer system. 控制部件从存储器中取出指令， 并确定其类型或对其进行 译码， 然后将每条指令分解成一系列简单的、 很小的步骤或动 作。这样，它就控制了整个计算机系统的每步操作。 2. The Arithmetic and Logic Unit The arithmetic and logic unit (ALU) is the functional unit that provides the computer with logical and computational capabilities. Data are brought into the ALU by the control unit, and the ALU performs whatever arithmetic or logic operations are required to help carry out the instruction. II 算术/逻辑部件chapter 1 Principles Of Computer Organization算术/逻辑部件（ALU）是为计算机提供逻辑及计算功能 的部件。控制部件将数据送到算术/逻辑部件中，然后由算术/ 逻辑部件完成执行指令所需的算术或逻辑操作。 Arithmetic operations include adding, subtracting, multiplying, and dividing. Logic operations make a comparison and take action based on the results. For example, two numbers might be compared to determine if they are equal. If they are equal, proc if they are not equal, processing will stop. 算术运算包括加、减、乘、除。逻辑运算完成比较，并根 据结果选择操作。例如，比较两个数是否相等，如果相等，则 继续处理；如果不等，则停止处理。 3. Registers A register is a storage location inside the processor. Registers in the control unit are used to keep track of the overall status of the program that is running. Control unit registers store information such as the current instruction, the location of the next instruction to be executed, and the operands of the instruction. In the ALU, registers store data items that are added, subtracted, multiplied, divided, and compared. Other registers store the results of arithmetic and logic operations. III 寄存器 寄存器是处理器内部的存储单元。 控制部件中的寄存器用 来跟踪正在运行的程序的总体状态， 它存储如当前指令、 下一 条将要执行的指令地址以及当前指令的操作数等信息。 在算术 逻辑部件中，寄存器存放要进行加、减、乘、除和比较的数据 项，而其他寄存器则存放算术运算及逻辑运算的结果。 An important factor that affects the speed and performance of a processor is the size of the registers. Technically, the term word size (also called word length) describes the size of an operand register, but it is also used more loosely to describe the size of the pathways to andchapter 1 Principles Of Computer Organizationfrom the processor. Currently, word sizes in general purpose computers range from 8 to 64 bits. If the operand registers of a processor are 16 bits wide, the processor is said to be a 16-bit processor.影响处理器速度和性能的一个重要因素是寄存器的大小。 技术上讲术语“字的大小” （也称字长）描述了操作数寄存器 的大小， 但它也可用来不那么严格地描述出入处理器的通道的 大小。现在，通用计算机的字长从8位到64位不等。如果处理 器的操作数寄存器是16位的，那么就称该处理器是16位处理 器。Keywords and Abbreviations:clock 时钟 processor 处理器 operation 操作、操作码指令 operand 操作数 register 寄存器 arithmetic and logic unit (ALU) megahertz (MHz) control unit Word size machine language 算术/逻辑部件 兆赫 控制部件 字长 机器语言Notes：[1]Every processor comes with a unique set of operations such as ADD, STORE, or LOAD that represent the processor's instruction set. 每个处理器都具有如加、存储或装入这样代表处理器指令集 的一组独特的操作集。 [2]The processor's job is to retrieve instructions and operands from memory and to perform each operation. 处理器的工作是从内存检索指令和操作数并完成每一个操chapter 1 Principles Of Computer Organization作。1.3 MEMORY SYSTEMS1. Memory System Desiderata The memory system has three desiderata. (1) Size: Infinitely large, no constraints on program or data set size. (2)Speed: Infinitely fast, latency equal to the fastest memory technology available. (3)Cost: The per bit cost should approach the lowest-cost technology available. Clearly these specifications cannot all be achieved as they are mutually exclusive[1]. However, with the semiconductor and magnetic memory technology of today, these specifications are closely approximated.1.3 存储系统I 存储系统需求 存储器系统有以下三项需求： （1）容量：无限大，对程序或者数据集大小没有任何约 束。 （2）速度：无限快，等待时间在现有存储器技术下是最 短的。 （3）价格：每位的价格在可使用的技术中应接近最低。 很明显，由于这三个需求相互制约，所以很难全部满足。 不过， 随着半导体和磁存储器技术的发展， 这些需求越来越接 近满足。chapter 1 Principles Of Computer Organization2. Hierarchical Memory In this section it is shown how designers implement a practical memory that approaches the performance of an ideal memory at reasonable cost. This memory system has a hierarchy of levels: The memory closest to the processor is fast and relatively small, but has a high cost per bit. This level The real memory, sometimes known as main memory, is slower, larger, and has a lower cost pe The lowest level in the hierarchy is usually a magnetic disk that has the longest latency and
however, it can be very large and has a very low cost per bit. This hierarchy is illustrated in Fig.1.3.Fig.1.3 Hierarchical MemoryNote that Fig.1.3 does not include the processor register file in the memory hierarchy. The register file is a program-managed cache and is generally not included in the memory system. Also, there can be more than one cache in the hierarchy.II 存储的层次结构 下面说明设计者如何在合理的价格下设计出性能理想的 实际存储器。 这一存储系统具有下述层次结构： 最靠近处理器 的是快速、容量相对小，但每位价格高的存储器，这一级叫做 高速缓冲存储器；下一级是实存储器，有时也称为主存储器， 是速度较低、容量较大、每位价格比高速缓存低的存储器；层 次结构中最低一层通常是等待时间最长， 带宽最窄的磁盘； 但 它的容量非常大，每位价格非常低，如图1.3所示。 图1.3 存储的层次结构chapter 1 Principles Of Computer Organization请注意，图1.3中没有包括存储器层次结构中的处理器寄 存器组。 寄存器组是程序控制的高速缓存， 一般不包括在存储 系统中。此外，在存储器层次中可以有不只一个高速缓存。 3. Paged Virtual Memory Paged virtual memory provides the solution to the first desideratum of a very large memory's being available to the processor. Because of the importance of this desideratum, the relationship between virtual and real memory is discussed first. With virtual memory, the processor addresses the disk, the large, slow end of the hierarchy. The memories between the processor and the disk are there to increase the effective performance (reduced latency and increased bandwidth) of the very slow disk. III 页式虚拟存储器 页式虚拟存储器为处理器可用的超大的存储器容量的需 求提供了解决办法。 由于这一需求很重要， 故先讨论虚拟存储 器与实存储器之间的关系。 处理器以虚拟存储器的方式访问位 于层次结构最底层的大容量、 低速磁盘。 在处理器和磁盘之间 放置存储器是为了提高低速磁盘的有效性能 （减少等待时间和 增加带宽）。 If every instruction and data reference were made to the disk, the processor performance would be slow indeed. Then why is virtual memory so important? Large memory is needed for large programs and data sets. Early computers with small real memory required that the transfer of data between real memory and disk be managed explicitly by the operating system or the user. Virtual memory provides for automatic management of this portion of the memory hierarchy through a combination of hardware and software aids[2]. 如果每条指令和数据引用都要访问磁盘， 则处理器的性能chapter 1 Principles Of Computer Organization必定很差。 那么为什么虚拟存储器如此重要？大型程序和数据集需 要大容量存储器。 早期的计算机实存储器容量很小， 要求由操 作系统或用户直接管理实存储器和磁盘之间的数据传送。 虚拟 存储器通过硬件和软件的结合自动地管理存储器层次结构的 这一部分。 The virtual memory interface is shown in Fig.1.4. A real memory of 16M bytes and a virtual memory of 2G bytes are sh many modern virtual- memory systems are much larger than this. Virtual-memory space is divided into equal- sized groups called pages. A page in a modern computer is 1K, 2K, or 4K bytes. Real memory is also divided into the same equal-sized groups, called page frames. When information is moved between virtual-memory space and real-memory space, a complete page is moved. 虚拟存储器接口如图 1.4 所示， 图中画出了 16MB 实存储 器和 2GB 虚拟存储器；现在很多虚拟存储器系统的容量都比 它大很多。 虚拟存储器空间被分成多个相同容量的组， 称为页 面。现在计算机的页面大小是 1KB、2KB 或 4KB。实存储器 也被分成多个容量相同的组， 叫做页帧。 信息是整页整页地在 虚拟存储器和实存储器之间传送的。 4. Caches Section 3 discussed how virtual memory extends the address space of a processor. However, the latency of real memory is too long to support high-performance processors. Even with the high-speed DRAMs used today for real memory, something must be done to overcome this latency problem. 4 高速缓冲存储器 第三部分讨论了虚拟存储器如何扩展处理器的地址空间。 但是实存储器的等待时间对高性能处理器来讲仍然太长。 即使chapter 1 Principles Of Computer Organization在目前很多实存储器采用高速动态随机存储器 （DRAM） 的情 况下，为了克服这一等待时问题，还得做一些工作。 The solution to this performance problem is to add another level to the memory hierarchy, called a cache, shown in Fig.1.3. The allocation of spaces in a three-level memory is shown in Fig.1.5. Generally, the virtual-address space is divided into equal-sized pages. These pages are placed in real-memory frames of the same size. Because a page can be placed in any vacant frame, there is no particular order to the allocation of pages to frames. With the addition of a cache, blocks of 16-32 bytes are taken from the page frames in real memory and placed into a block slot for access by the processor. For modern processors the cache usually has a latency of one processor clock, so that instructions and data may be fetched without delay except when the referenced item is not in the cache.Fig. 1.4 Page allocation and address translationchapter 1 Principles Of Computer Organization Fig.1.5 Real memory and cache allocation解决这一性能问题的方法是在存储层次结构中加入另外 一层，称为高速缓冲存储器，如图1.3所示。图1.5显示了3级存 储空间分配。通常，虚拟地址空间被分为大小相同的页，这些 页放在大小相同的实存储器的帧中。 因为一页可以放在任何空 帧中， 因而对于帧而言页的放置没有具体顺序的要求。 当加入 了高速缓存之后，实存储器中的页帧就分成多个16~32B的数 据块，这些块放到高速缓存中的块存取窗口中供处理器访问。 现在的处理器中， 高速缓存的等待时间只占一个处理器时钟周 期， 所以取数和取指令没有时延， 除非要访问的数据项不在高 速缓存中。 图 1.5 实存和高速缓存分配 5. Memory Devices (1) Random-Access Memory Random-access memory, or RAM, is the kind of memory we usually refer to when we speak of computer memory. It is the most widely used type, and consists of rows of chips with locations established in tables maintained by the control unit. 5 存储器设备 （1）随机存储器 随机存储器或称 RAM，是人们常说的计算机存储器。它 是使用最广的一种类型， 由一组芯片构成， 其存储单元由控制 部件中的地址表管理。 As the name suggests, items stored in RAM can be gotten (accessed) both easily and in any order (randomly) rather than in some sequence. RAM relies on electric current fo moreover, if the power is turned off or interrupted, RAM quickly empties itself of all your hard work. Thus, we say RAM is volatile, or nonpermanent.chapter 1 Principles Of Computer Organization顾名思义，RAM中的内容可以很容易地以任意顺序（随 机地）读出（或称访问），而不用考虑什么先来后到。RAM 始终靠电流进行操作；而且，如果电源关闭或中断，RAM会 很快丢失人们辛辛苦苦存入的内容。因此人们把RAM称为易 失性或非永久性的存储器。 (2) Read-Only Memory Read-only memory, or ROM, typically holds programs. These programs are manufactured or &hard-wired& in place on the ROM chips. For example, a microcomputer has a built-in ROM chip that stores critical programs such as the one that starts up, or &boots&, the computer. ROM is &slower& than RAM memory, and as a result, items in ROM are transferred to RAM when needed for fast processing. （2）只读存储器 只读存储器或 ROM，主要用来存储程序。这些程序是做 在 ROM 芯片中或者说通过硬连线实现的。 例如在微型计算机 中就有内置 ROM 芯片（有时称为 ROM BIOS，即 ROM 基本 输入输出系统），该芯片存储一些关键的程序，如计算机的启 动或引导程序。ROM 的读取速度比 RAM 慢，因此如果需要 快速处理，则将 ROM 中的内容传送到 RAM 中。 Items held in ROM can be read, but they cannot be changed or erased by normal input methods. New items cannot be written into ROM. The only way to change items in most forms of ROM is to change the actual circuits. ROM 中的内容可以读，但不能用一般的输入方法更改或 擦除。新内容也不能写入 ROM。在大多数型号 ROM 中改变 内容的惟一方法是更换实际电路。 (3) Magnetic Disks The magnetic disk is a circular platter with a smooth surface and a coating that can be magnetized. Data is stored on it as magnetizedchapter 1 Principles Of Computer Organizationspots. The reading and recording device, the disk drive, spins the disk past read/write heads that detect or write the magnetized spots on the disk.（3）磁盘 磁盘是一个表面光滑且涂敷可磁化材料的圆盘。 数据在磁 盘上作为磁化点存入。 读出与记录设备即磁盘驱动器驱动磁盘 转动， 当通过读写磁头时， 磁头从磁盘上的磁化点检测出或写 入信息。 (4) CD-ROMS Optical disks need thin beams of concentrated light to store and read data. It is a form of laser storage, called CD-ROM. There are two types of optical disks that can be user-recorded: WORM and erasable optical. WORM stands for &write once, read many&: Data can be written to this disk just one time, but the data can be read many times. Erasable optical disks can be written to, read, and erased. （4）只读光盘 光盘用细聚光光束去存储和读出数据。 只读光盘是激光存 储器的一种形式。 用户使用的可读写光盘有两种类型：WORM和可擦除的 光盘。WORM代表一次写多次读：数据只能写入一次但可读 出多次。可擦除光盘可以读、写和擦除。 (5) Magnetic Tape A magnetic tape is a narrow plastic strip similar to the tape used in tape recorders. The tapes are read by tape drive moving the tape past a read/write head, which detects or writes magnetized spots on the iron-oxide coating of the tape. Each pattern of spots matches the byte code for character being stored. （5）磁带chapter 1 Principles Of Computer Organization磁带是一种类似于录音磁带的窄塑料带。 由磁带驱动器去 读磁带的内容。 驱动器驱动磁带， 由读写磁头检出或写入由氧 化铁涂敷的磁化点， 以各磁化点的不同极性表示所存储字符的 二进制代码。Keywords and Abbreviations:hierarchical memory magnetic disk disk drive register file page frame magnetic tape cache Main memory floppy disk (diskette) latency real memory (storage) paged virtual memory Dynamic RAM (DRAM) Read-Only Memory (ROM) Compact Disk ROM (CD-ROM) write once, read many (WORM) Random-Access Memory (RAM) 存储器层次结构 磁盘 磁盘驱动器 寄存器组 页帧 磁带 高速缓冲存储器 主存储器 软磁盘 等待时间 实存储器 页式虚拟存储器 动态随机储器 只读存储器 只读光盘 一次写，多次读 随机（访问）存储Notes：[1]Clearly these specifications cannot all be achieved as they are mutually exclusive.chapter 1 Principles Of Computer Organization很明显，在不能共存的情况下，这些技术指标是不能完全达 到的。 [2]Virtual memory provides for automatic management of this portion of the memory hierarchy through a combination of hardware and software aids. 虚拟存储器在硬件与软件的共同帮助下实现了对内存结构 的自动化管理。1.4 Input/Output SystemProcessors need a source of input data and a destination for output data. Processors also require storage space for large volumes of intermediate data. Thus the I/O system provides these storage facilities by connecting the processor’s memory to the I/O devices, these devices vary widely in l thus, a major function of the I/O system is to match their latencies and bandwidths to that of the memory system. I/O devices consist of such diverse items as keyboards, modems, and hard disks. Each of these devices has its own latency and bandwidth requirements that must be satisfied for a properly functioning system[1].1.4 输入/输出系统处理器需要有输入数据的源设备和用于数据输出的目的 设备。它还要求有存储大量中间数据的存储空间，I/O系统就 是通过把处理器的存储器与I/O设备连接起来的存储设施。这 些设备在等待时间和带宽上是大不相同的；因此I/O系统的主 要功能是使其在执行时间和带宽上与存储系统协调起来。I/O 设备包括键盘、 调制解调器和硬盘等多种设备。 对每种设备自chapter 1 Principles Of Computer Organization身的等待时间和带宽，必须满足系统正确操作的要求。 The major tasks of the I/O system are the following ? to establish the connection between the memory and the I/O ? to synchronize and manage the control
? to provide buffering when the source and sink bandwidths
? to perform code con ? to interrupt the pro ? to terminate the operation when it is completed. I/O系统的主要任务是： （1）建立存储器和I/O设备之间的连接； （2）对数据传输的控制进行同步化与管理； （3）当信源和信宿的带宽和等待时间不同时，提供缓存 功能； （4）需要时完成代码的转换； （5）需要时中断处理器的工作； （6）任务完成时终止操作。 These tasks are accomplished by hardware and software, in varying amounts of each. The more hardware-oriented, the higher the performance and the higher the hardware cost. The more software-oriented, the lower the performance and the lower the hardware cost. Control can be classified into two broad categories, programmed I/O and coprocessor I/O. 这些任务都是通过硬件和软件完成的， 不过对硬件或软件 的依赖程度各不相同。越是依靠硬件，则性能越高，硬件成本 越大；越是依靠软件，则性能越差，硬件费用越低。控制方法 可以分为两大类：程序控制I/O和协处理器I/O。 1. Programmed I/Ochapter 1 Principles Of Computer OrganizationAlso known as direct I/O, is accomplished by a program executing on the processor itself to control the I/O operations and transfer the data. With programmed I/O, shown in Fig.1.6 there are several architectural register (minimally an input register and an output register) that are addressed by special move instructions.Fig.1.6 Programmed I/OThese move instructions move information from the accumulator (or general- purpose register) to/from the I/O registers. The peripherals are connected directly to the bits of these registers.1.程序控制I/O 程序控制I/O，又称直接I/O，由在处理器上执行的程序去 控制I/O操作和传送数据。如图1.6所示的程序控制I/O，有几个 体系结构寄存器（至少1个输入寄存器和1个输出寄存器），它 们由专用的传送指令寻址。 图1.6 程序控制I/O 这些传送指令在累加器（或通用寄存器）和I/O寄存器之 间传送信息，而外围设备直接与每个寄存器的位相连。 2. Memory-Mapped I/O Memory-Mapped I/O is another form of programmed I/O that maps the device connections to bits in memory address space, as shown in Fig.1.7. An output command is a normal store instruction that stores a pattern of bits into a design an input command is a normal load instruction that reads a memory location.chapter 1 Principles Of Computer OrganizationFig.1.7 Memory-mapped I/OMemory-mapped I/O requires the full participation of the processor, as with programmed I/O. Thus there is a similar loss of efficiency that is due to executing the I/O control program.2.存储器映射I/O 存储器映射I/O是另一种程序控制I/O， 它把I/O设备连接映 射成存储器地址空间中的位组，如图1.7所示。输出命令是一 条普通的存储指令， 把位模式存入指定的存储单元中。 输入命 令是一条普通的从指定存储单元装入（读取）数据的指令。 图1.7 存储器映射I/O 像程序控制I/O一样，存储器映射I/O也要求处理器全面参 与。由于要执行I/O控制程序，故效率同样降低。 The Intel Pentium Pro supports memory-mapped I/O in addition to programmed I/O. Any of the processor's instructions that reference memory can address memory- mapped I/O locations. Intel Pentium Pro 在支持程序控制 I/O 的同时，也支持存储 器映射 I/O。任何访问内存的处理器指令都能访问存储器映射 I/O 地址。 The move instruction can transfer data between any of the processor's registers and the spaces in memory allocated for I/O. Other operations such as ADD, AND, OR, and test can also have one source argument in I/O space. The logical operations are useful for control of bits in the control and status registers of an I/O device that is mapped into one or more of the memory-address spaces.chapter 1 Principles Of Computer Organization传送（移动）指令可以在任何处理器、寄存器和为I/O分 配的内存空间之间传送数据。其他操作如“加（ADD）”、 “与（AND）”、“或（OR）”以及测试，也可以有一个I/O 空间的源参量。逻辑操作常用于对I/O设备中的控件和状态寄 存器的位进行控制，而每一设备都可以映射为1个或多个存储 器地址空间。 3. Interrupt I/O Because of the low efficiency of pure programmed or memory-mapped I/O in high- performance system, so interrupt is produced. Early mainframe computers, such as the Univac 1103 and the IBM 701 were users of this technique. The processor sends a command to the device, usually by means of a special programmed I/O register, to start its operation. After the request is made to the device, the processor returns to the main program. When the latency is satisfied and the device is ready to transfer, the device sends an interrupt signal to the processor and the processor services the interrupt and performs the data transfer. Various status reports are sent from the device to the processor by means of the programmed I/O paths. Interrupt I/O can be used with both programmed and memory-mapped I/O；The Intel Pentium Pro implements both techniques. 3.中断I/O 由于对高性能系统来说纯程序控制I/O或存储器映射I/O 的效率都很低，所以又出现了中断方式。早期的大型计算机， 如Univac 1103，IBM 701都采用中断技术。 处理器通常使用专用的程序控制I/O寄存器向设备发送一 个启动设备操作的命令。 在向设备发出请求之后， 处理器返回 到主程序上。当等待时间满足要求并且设备做好传送准备时， 它向处理器发送一个中断信号， 处理器进行中断服务并完成数chapter 1 Principles Of Computer Organization据传送。借助程序控制I/O通道，从设备向处理器送出各种状 态报告。 中断I/O可以与程序控制I/O和存储器映射I/O一起使用； Inter Pentium Pro（英特尔奔腾处理器）就采用了这两种技术。 4. Coprocessor I/OWhen the processor is being used to control I/O and move the data, there is a loss of processor efficiency. Thus the idea naturally arises to use a second processor or coprocessor for I/O. The autonomous coprocessor first appeared in the IBM 709 in 1959, and it performed all the I/O tasks and freed the main processor for its tasks. Fig.1.8 shows a coprocessor connecting an I/O device to the system bus. Control and status information is passed between the processor and the coprocessor by means of paths similar to those of programmed I/O. The processor sends a command to the coprocessor that autonomously performs the I/O operation. The introduction of a coprocessor makes this configuration a multiprocessor. The problems of any multiprocessor must be addressed with coprocessor I/O. These Problems include software synchronization, hardware synchronization, memory protection, and memory coherency. There are two general types of these coprocessors: programmed I/O channel and direct memory access (DMA).Fig.1.8 Coprocessor I/O协处理器I/O 当处理器用于控制I/O和传送数据时，其效率下降。因而 自然会想到用第二个处理器或协处理器去处理I/O。1959年在 IBM 709机器上第一次使用自主协处理器，由该协处理器完成chapter 1 Principles Of Computer Organization所有I/O任务，而让主处理器去完成它自己的任务。图1.8显示 了协处理器将I/O没备连接到系统总线的情况。通过类似于程 序控制I/O那样的通道，在处理器和协处理器之间传送控制和 状态信息。 处理器向协处理器发送一个命令， 由协处理器自主 完成I/O操作。 采用协处理器使这种配置成为多处理器结构。协处理器 I/O也必然会有其他多处理器一样的问题。这些问题包括软件 同步、硬件同步、存储器保护和存储器相关等。 协处理器有两大类型：程序控制I/O通道和直接存储器存 取（DMA）。 图1.8 协处理器I/O 5. I/O devices(1) INTERACTIVE INPUTThe idea of interactive input is to capture information directly into computers and get responses from computers as the input occurs. This happens when you type on a keyboard and immediately see the results of your work on a screen. It is so called as &screen-dependent&.5.输入/输出设备 交互性输入 交互性输入是指当向计算机输入信息时， 获取直接输入计 算机的信息，并从计算机得到响应。例如，当你敲键时，立即 在屏幕上看到敲键的结果。所以这又叫做屏幕相关型输入。 Keyboard entry may be too slow or awkward for some jobs, but the keyboard can be bypassed by using one of a number of other interactive devices. Most of today's microcomputers, for example, include a mouse or a trackball that lets you use natural arm or hand motions to move the cursor. 对于某些任务， 键盘输入太慢或使用不便， 因而可以不用 键盘，而采用很多其他交互性输入设备。例如，目前大多数微chapter 1 Principles Of Computer Organization型计算机都配有鼠标或跟踪球， 这就可以用手臂或手的自然运 动去移动光标了。 Some screens themselves accept interactive input: The touch screen looks like a normal computer screen, but it can detect the point at which you touch it. 某些屏幕本身可以接收交互性输入： 例如， 虽然触摸屏看 上去像普通的计算机屏幕，但它可以检测到你触摸的那一点。 Technical applications such as graphic arts, mapping, and engineering often require specialized input methods. Perhaps the most natural tools are the light pen and the graphics tablet or digitizer. 诸如图形艺术、 映像和工程等的技术应用通常需要一些专 门的输入方法。 光笔和图形输入板或数字化仪这几种工具应该 是使用最多的了。(2) DIRECT INPUTIn an information system, the greatest majority of delays, errors, and problems occur during the input phase. To attack the problem, a number of methods have been developed to increase speed, accuracy, and reliability of input. Collectively, these techniques have been referred to as source data automation. Scanning, voice input, and sensor input are three types of direct input.直接输入 在信息系统中，大多数的延时、错误和问题发生在输入阶段。 为解决这一问题， 研究出了很多提高输入速度、 精确度和可靠 性的方法。综合地说这些方法可以称为源数据自动化。扫描、 声音输入和传感器输入是三种直接输入类型。 Scanners, also called optical scanners, are devices that read printed material so that it can be put in computer-readable form without your having to retype, redraw, reprint, or re-photograph the material.chapter 1 Principles Of Computer Organization扫描仪， 又称光学扫描仪， 是一种用于读取印刷品上信息 的设备， 因而， 印刷品上的信息可以变成计算机能够读的形式 输入到计算机中，而无须对这些信息再录入、重画、重新打印 或重新照相。(3) SPEECH RECOGNITIONSpeech-recognition or voice-input devices accept spoken words through a microphone and change the sounds into computer-readable signals.语音识别 语音识别， 又称声音输入， 这种设备能通过麦克风接收话 音并将其转化为计算机能识别的信号。(4) SENSOR INPUTHome computer users may link their systems to thermometers, light detectors, and motion detectors to help control energy use and deter vandalism. Input from these detectors is called sensor input. Sensor input is used widely with microcomputers in factories and in scientific and medical laboratories, too.传感器输入 家庭电脑用户大概希望将他们的计算机系统与温度计、 光 探测器和监视器连接起来， 以便控制能源的使用和防止外人非 法入侵。 这些探测器的输入信息称为传感器输入。 传感器输入 也广泛用于工厂、科研部门和医疗部门的微型计算机上。(5) DISPLAY OUTPUTSThe most common output device is the monitor, a cathode-ray tube (CRT) that is basically a television tube adapted to present text, data, or images generated by computers. High-quality color monitors receive three separate color signals (red, green, and blue) and thus are called RGB color monitors. The clarity or sharpness of the display is termed resolution. The resolution of a monitor indicates the number of imagechapter 1 Principles Of Computer Organizationpoints, or pixels (picture elements), on its screen.显示输出 最常用的输出设备要算监视器了， 它是一种与电视机显像 管基本相似的阴极射线管（CRT），用于显示由计算机产生的 文本、 数据或图像。 高性能彩色监视器接收三种颜色信号 （红、 绿和蓝）并称之为 RGB 彩色监视器。显示器的清晰度，其术 语叫做分辨率。 监视器的分辨率表明屏幕上的图像点或像素的 数量（像素是图形单元）。 The flat-panel displays used on portable computers are less bulky and require less power than CRT monitors. A common electronic imaging technique used in flat-panel displays is liquid-crystal display (LCD). Two other flat-panel displays are the gas plasma display, which uses electric current to cause gases to glow, and the electroluminescent display (ELD), which is similar to gas plasma but has layers of phosphor rather than gas[2]. 用于便携式计算机上的平面显示器比 CRT 监视器体积 小， 耗电少。 用于平面显示器的一种常用的电子显像技术是液 晶显示 （LCD）。 另外两种平面显示器是气体等离子显示器和 场致发光显示器（ELD），前者用电流使气体发光，后者与气 体等离子体相似，但激发的是若干磷涂层而不是气体。(6) PRINTERS FOR DOCUMENT OUTPUTSDocument outputs are produced on printers and plotters, devices that produce images or text on paper. These outputs are known as printouts or hard copy. Printers and plotters are classified by several criteria， one of them is on impact and non-impact printing methods.文件输出打印机 文件是在打印机和绘图仪上输出的， 这两种设备在纸上生chapter 1 Principles Of Computer Organization成影像或文本。这种输出称为打印输出或硬拷贝。 打印机和绘图仪可按几种方法分类， 其中之一是按接触或 非接触式打印来分类。(7) IMPACT PRINTERSA common impact printer for microcomputers is, the dot-matrix printer, which works by striking pins in a print element against the ribbon and paper. The pins are formed into a matrix, and different combinations of pins in the matrix shape the character or image.接触式打印机 微型计算机常用的接触式打印机是点阵式打印机， 它是驱 动装在打印头上的打印针， 对着色带和纸打印的。 多个针构成 一个矩阵，而矩阵中针的不同组合形成了字符或图像。(8) NON IMPACT PRINTERSNon impact printers use heat, laser, or spraying techniques to print characters and images. The two major non impact technologies in use today are ink-jet and laser.非接触式打印机 非接触式打印机采用热、 激光或喷墨技术来打印字符和图 像。 目前使用的非接触式打印技术主要有两种： 喷墨和激光打 印。Keywords and Abbreviations:latency 等待时间 modem 调制解调 coprocessor I/O 协处理器 I/O bandwidth hard disk programmed I/O 带宽 硬（磁） 程序控制 I/Ochapter 1 Principles Of Computer Organizationinterrupt 中断 multiprocessor 多处理 coherency 相关，相干 channel 信道，通道 buffering 缓冲 peripheral 外围，外围设备 load 装入，加 direct memory access(DMA)memory-mapped I/O path synchronization input/output system accumulator pattern of bits code conversion 直接存储器存取存储器映射 I/O 通路，路径 同步化 输入输出系 累加器 位模式 代码转换Notes：[1] Each of these devices has its own latency and bandwidth requirements that must be satisfied for a properly functioning system. 每个设备都具有为满足系统正常运行所必须满足的时延和 带宽要求。 [2] Two other flat-panel displays are the gas plasma display, which uses electric current to cause gases to glow, and the electroluminescent display (ELD), which is similar to gas plasma but has layers of phosphor rather than gas. 其它两种平板显示设备分别是利用电流使气体发光的气体 等离子体显示器和类似气体等离子但使用是荧光粉而非气体的电 发光显示器。1.5 Buses and ControllersMost modern computers use a bus, or buses, for interconnecting the major components of the system. A bus serves as a pathway between components for passing address, instructions, and data. A simplechapter 1 Principles Of Computer Organizationhigh-level view of a bus is shown in Fig.1.9. This is the bus shown in Fig.1.8 that is used with the coprocessor I/O. This bus interconnects the processor, main memory, and I/O devices by means of their controllers.Fig.1.9 Simple bus structureBuses can be classified in a number of ways. By purpose, control, and communication technique. 大多数现代计算机用一条或多条总线连接系统的各主 要部件。总线的作用是为各个部件之间传送地址、指令和数据提 供通路。 图 1.9 是总线的高层简单视图。 这是图 1.8 中用于协处理 器 I/O 的总线。这一总线由控制器将处理器、主存储器和 I/O 设 备连在一起。 图 1.9 简单总线结构 总线可以按多种方式分类，即按目的，按控制方法和按通信 技术分类。 1. Dedicated or general purpose The major difference between dedicated and general-purpose buses is that a dedicated bus is point-to-point between two physical devices, whereas a general-purpose bus interconnects more than two physical devices[1]. Fig.1.10 illustrates the two types. Dedicated buses are used in cases in which the latency and the bandwidth requirements are such that sharing the bus with another user can result in unacceptable system performance. Note that a dedicated bus does not need address lines because the source and destination are addressed by implication. That is, device 1 always sends to device 2 or device 2 to device 1.chapter 1 Principles Of Computer OrganizationSome dedicated buses are unidirectional with information flow in only one direction. For example, the bus that connects a memory to a graphics controller may be unidirectional.Fig.1.10 Dedicated and general-purpose busesI 专用或通用 专用与通用总线的主要区别为：专用总线是两个物理设备之 间的点对点连接，而通用总线连接多于两个物理设备。图 1.10 展 示了这两种连接类型。当与另一个用户共享总线时，如果由于等 待时间和带宽要求得不到满足使系统性能下降得不能忍受时，须 采用专用总线。注意，由于在专用总线中，源和目的地址是隐含 的，所以不需要地址线。也就是设备 1 总是向设备 2 发送信息或 相反。某些专用总线是单向的，信息流只有一个方向。例如，连 接存储器和图形控制器的总线就可以是单向的。 图 1.10 专用和通用总线 Because dedicated buses are used internal to the processor or for special high-bandwidth applications without general-purpose capabilities, these buses are not considered further. Instead, the following paragraphs discuss the control and communications design techniques found with general-purpose buses. 由于专用总线用于处理器内部，或用于不需要通用功能的大 带宽专用系统，因而我们对这些总线不做进一步讨论。相反，下 面将讨论通用总线中的控制和通信设计技术。chapter 1 Principles Of Computer OrganizationAlso, with a general-purpose bus, a number of users share the same bus and simultaneous requests for the bus are resolved by one of a number of resolution techniques. Some of the devices on a general-purpose bus are both senders and receivers or only senders or only receivers. For example, a printer controller's primary function is to receive data and send some status information. A disk controller, on the other hand, sends and receives data and sends status information. 同样，对于通用总线，多个用户共享同一条总线，当他们同 时对总线提出请求时，可采用多种技术中的一种加以解决。通用 总线上的某些设备可以既是发送器又是接收器，也可以只是发送 器，或只是接收器。例如，打印机控制器的主要功能是接收数据 并发送某些状态信息。而磁盘控制器既要发送和接收数据，又要 发送状态信息。 2. Centralized or Decentralized Control The control of a general-purpose bus can be either centralized or decentralized. The basic requirement is to grant or not grant a device access to the bus. With centralized or decentralized control, all devices are treated equally except for their priority of access. II 集中式或分散式控制 通用总线的控制既可以是集中式，也可以是分散式。其基本 要求是授予还是不授予设备对总线的访问权。除了访问总线的优 先级以外，集中式和分散式控制对待所有的设备都是一视同仁 的。 Thus, if one of the devices is the processor, it may be given the highest priority for bus access. However, in some systems an I/O device may have the highest priority because of the loss i for example, if a disk is unable to read and misses a complete revolution, many milliseconds will be lost.chapter 1 Principles Of Computer Organization因此，如果设备是处理器，则应给它以总线访问的最高优先 级。但是在某些系统中，为避免对系统性能的损害，让某种 I/O 设备具有最高优先级。例如，磁盘若转动一圈内还读不出数据， 则损失很多时间。 Centralized Control. A single hardware control unit will recognize a request and grant access to the bus to a requesting device. It is the responsibility of the controller to resolve simultaneous requests and assign priority to the requests. At least three designs are used for centralized controllers: daisy chain, polling with a global counter, and polling with local counters. 集中式控制。用一个控制器硬件去识别总线请求并允许请求 设备去访问总线。该控制器的责任是处理同时来的多个请求并对 这些请求安排优先级。 集中式控制器至少有 3 种方式： 菊花链式、 带全局计数器的轮询和带局部计数器的轮询。 Distributed Control. Distributed control, also known as decentralized control, distributes the control function between all the devices on the bus. The major advantage of decentralized control is that the system is easily expandable by the addition of modules. As with centralized control, there are three basic designs: daisy chain, polling, and independent requests. 分布式控制。分布式控制又称分散式控制，它把控制功能分 布在总线上的所有设备中。分散式控制的主要优点是通过增加模 块使系统容易扩充。与集中式控制一样，分散式控制也有 3 种基 本方式：菊花链、轮询和独立请求。 3. Synchronous or Asynchronous Communication The transmission of addresses, control information, and data between two devices may be synchronous with a clock, or asynchronous without a clock and self-timed. III 同步或异步通信chapter 1 Principles Of Computer Organization地址、控制信息和数据在两个设备之间可以用一个时钟同步 传送，或不用时钟，而用自身的定时器实现异步传送。 Synchronous Communication. A simplified diagram of a synchronous bus (the data and clock portion) connected between two devices is shown on the left of Fig.1.11. Data are to be transmitted between the card in the right-hand slot to the card in the left-hand slot. The transmitter and the receiver are clocked from a common source on the left-hand card. 同步通信。连接两个设备的同步总线（数据和时钟部分）简化框 图如图 1.11（左） 所示。 数据从右边槽中的卡传向左边槽中的卡。 发送器和接收器用左边卡上的公共时钟源同步。 图 1.11 同步总线时钟 Asynchronous Communication. Asynchronous communication for buses was developed to overcome the worst-case clock rate limitations of synchronous systems. With asynchronous communications, data transfers occur at the fastest rate and smallest delay possible under the circumstances of the physical status of the bus. As cards are added to the bus, the timing automatically adjusts for each card. There are a number of as however, only one of the simpler ones is discussed here. 异步通信。总线的异步通信是为了克服同步系统中极差的时 钟频率限制而开发的。异步通信中，数据在总线的物理状态环境 下以最快的速率和最小的时延传送。当一些卡加到总线上时，会 自动为每一卡调整时钟。异步协议有很多种，这里只讨论比较简 单的一种。chapter 1 Principles Of Computer OrganizationFig.1.11 Synchronous bus clockingThe timing diagram for an asynchronous exchange is shown in Fig.1.12. This figure illustrates the action when a source sends data to a destination.Fig.1.12 Asynchronous transfer图 1.12 为异步交换时序图， 该图说明了当发信方向接收方发 送数据时的工作过程。 图 1.12 异步交换（时序图） 4. Bus Design Examples Table1.3 provides examples of the four general-purpose bus types from the taxonomy: centralized and decentralized control and synchronous and asynchronous communications.Table 1.3 General-purpose bus design exampleschapter 1 Principles Of Computer Organization Control Centralized Centralized Decentralized Decentralized Communications Synchronous Asynchronous Synchronous Asynchronous Examples PCI IPI Multibus 11 VME Future Bus Specification PCI SIG v2.1. ANSI X3.129 ANSI/IEEE 1296 IEEE 1014 IEEE 896.1Ⅵ 总线设计举例 表 1.3 从分类学角度给出了 4 种通用总线类型： 集中式和分散 式控制及同步和异步通信。 表 1.3 通用总线设计实例 PCI The peripheral component interconnect (PCI) is a recent high-bandwidth, processor-independent bus that can function as a mezzanine or peripheral bus[2]. Compared with other common bus specifications, PCI delivers better system performance for high-speed I/O subsystems (e.g., graphic display adapters, network interface controllers, disk controllers, and soon). The current standard allows the use of up to 64 data lines at 33 MHz, for a raw transfer rate of 264 Mb/s, or 2.112 Gb/s. But it is not just a high speed that makes PCI attractive. Economically, PCI is specifically designed to meet the I/O requirement of modern systems ； It requires very few chips to implement and supports other buses attached to the PCI bus. PCI 外围部件互连（PCI）是一种近来使用的大带宽、独立于处 理器的总线，可以作为底层或外围总线。与其他通用总线规范比 较，PCI 为高速 I/O 子系统（如图形显示适配器、网络接口控制 器、磁盘控制器）提供更好的系统性能。现在的标准在 33MHz 主频时， 可使用多达 64 条数据线， 原数据传输速率可达 264Mb/s，chapter 1 Principles Of Computer Organization或 2.112Gb/s。PCI 不仅因高传输速率而具有吸引力，它还是为满 足低价位的现代系统而专门设计的；要求很少的芯片即可实现并 支持与 PCI 总线连接的其他类型总线。Fig.1.13 Example PCI ConfigurationsPCI is designed to support a variety of microprocessor-based configurations, including both single- and multiple-processor systems. Accordingly, it provides a general-purpose set of functions. It makes use of synchronous timing and a centralized arbitration scheme. Fig.1.13(a) shows a typical use of PCI in a single-processor system. A combined DRAM controller and bridge to the PCI bus provides tight coupling with the processor and the ability to deliver data at high speeds. The bridge acts as a data buffer so that the speed of the PCI bus may differ from that of the processor's I/O capability. In a multiprocessor system (Fig.1.13 (b)), one or more PCI configurations may be connected by bridges to the processor's system bus. Thechapter 1 Principles Of Computer Organizationsystem bus supports only the processor/cache units, main memory, and the PCI bridges. Again, the use of bridges keeps the PCI independent of the processor speed yet provides the ability to receive and deliver data rapidly. 图 1.13 PCI 配置实例 PCI 支持各种基于微处理器的配置，包括单处理器系统和多 处理器系统。相应地，它提供一套通用功能，并采用同步定时和 集中仲裁机制。 图 1.13（a）展示了 PCI 在单处理器系统中的典型应用。连 向 PCI 总线的动态随机存储器（DRAM）控制器和桥接器的组合 与处理器紧密耦合，具有高速数据传输能力。桥接器的作用相当 于数据缓冲器，用于解决 PCI 总线速度与处理器 I/O 能力不匹配 的问题。在多处理器系统中（如图 1.13（b）所示）可通过桥接器 把 1 个或多个 PCI 配置与处理器系统总线相连。系统总线只支持 处理器-高速缓存部件、主存储器和 PCI 桥接器。再者， 桥接器的 使用让 PCI 与处理器速度无关，却带来了数据接收和发送的高速 度。Keywords and Abbreviations:bus 总线 synchronous 同步的 adapter 适配 timing 定时 chip 芯片 polling 轮询 Interconnect (PCI) dynamic RAM (DRAM) clock 时钟 asynchronous 异步的 decentralized 分散式（的） distributed 分布式（的） priority 优先级 daisy chain 菊花链 外围部件互连（总线） 动态随机存储器chapter 1 Principles Of Computer OrganizationNotes：[1] The major difference between dedicated and general-purpose buses is that a dedicated bus is point-to-point between two physical devices, whereas a general-purpose bus interconnects more than two physical devices. 专用和通用总线的主要差异在于专用总线是两个设备点对 点的连接而通用总线是不只两个物理设备互联。 [2]The peripheral component interconnect (PCI) is a recent high-bandwidth, processor-independent bus that can function as a mezzanine or peripheral bus. PCI 总线是一种新的能够以中间或外围总线形式起作用高带 宽且与处理器无关的的总线结构。1.6 USB―Universal Serial BusThe Universal Serial Bus is one of the fastest-growing and most widely accepted expansions to the personal computer in recent memory. It is impossible to buy an Intel-based PC (which makes up 94% of the personal-computer market) without a Universal Serial Port Bus. This is not to say that the USB is limited to the PC world, not by any stretch. Every computer hardware manufacturer is now acting to implement the Universal Serial Bus on its own platform. 在最新的存储器中，通用串行总线是对于个人计算机增长速 度最快和最广泛接受的扩展。没有一个通用串行总线是不可能的 购买基于英特尔处理器的电脑（它占据了 94 ％的个人电脑市 场） 。这并不是说个人计算机世界限制了 USB 接口，没有任何扩chapter 1 Principles Of Computer Organization展。每台计算机的硬件制造商现在是代理执行通用串行总线自己 的平台。 Why the sudden interest in something as seemingly trivial as a serial port？The answer is that the Universal Serial Bus is much more than a serial port―it's a serial bus. This means that a single port on the back of your computer can be the window (no pun intended) into a myriad of devices. Devices can be daisy-chained together. Groups of devices can be separated by concentration hardware called a hub. When you think of the Universal Serial Bus, it's best to think of it as a &network& of device, much as you would think of the Ethernet network. Chaining a bunch of devices together might not seem like such a good thing at first glance. In fact, it might seem like a downright bad idea for a lot of devices to share what little bit of bandwidth serial devices have traditionally had to work with. After all, there is barely enough bandwidth on an RS-232 port to get a decent connection to a printer. There certainly isn't enough to talk to a digital camera to download images. 为什么突然有兴趣的东西作为看似琐碎的串行端口吗？答 案是， 通用串行总线不仅仅是一个串行端口， 这是一个串行总线。 这意味着，在您的计算机后面有一个单独的端口可以作为窗口连 接到各种设备 （没有双关语意） 。 设备可以菊花链在一起。 设备群 可以被一个称为 hub 的集成硬件分开。 当你想到的通用串行总线， 最好把它作为一个“网络”的设备，就像你可能会认为的以太网 网络。乍一看链一堆设备可能似乎并不是一件好事。事实上，它 可能看起来像是一个彻头彻尾的坏主意让很多设备来分享历来一 直工作的串行设备的一点带宽。毕竟，几乎没有足够带宽的 RS 232 端口获得连接打印机。这肯定是不够的，就像谈论用数码相 机下载图像一样。 The Universal Serial Bus operates at over 10 million bits perchapter 1 Principles Of Computer Organizationsecond-this is the speed of the computer network in most businesses. The Universal Serial Bus is not considered &fast& when compared to things such as the Fiber Channel serial bus, which clocks in at about 300 million bits per second, or to upcoming bus technologies such as the IEEE 1394 &FireWire& bus to control audio and video sources that are &broadcast quality&[1]. So we will accept that the USB is a &mid-speed& bus and move on. 在大多数企业的高速计算机网络中通用串行总线运行超过 1000 万比特每秒。当与象每秒 300 百万位的光纤串行总线和象 IEEE 1394&FireWire&总线这样用来控制音频和视频资源的未来的 总线技术相比较，不能认为它是高速的总线。所以，我们将接受 的是， USB 是一种在移动的“中速”总线。 The Universal Serial Bus was designed with the thought of providing pure digital audio, video, and telecommunications to the modern computer user. The speed of the bus is more than sufficient to support these types of devices. 通用串行总线的设计思想是向现代计算机用户提供纯数字 音频，视频和电信。总线的速度足以支持这些类型的设备。 A big problem with personal computers has always been connecting to the peripherals that you want to use. Everything always seems to need its own adapter card plugged into the bus. There are video cards for high-resolution video. There are game cards to drive your joysticks. There are sound cards to drive speakers and there are video-input cards to bring video into the computer. The list goes on and on. 一个大的问题是你想用的外设一直连接着个人电脑。似乎总 是需要有自己的适合的卡片插入到总线上。有高清晰度视频的视 频卡。有驾驶您的操纵杆的游戏卡。有声卡去驱动扬声器，有视 频输入卡，可以使影片到计算机中。例子举不胜举。chapter 1 Principles Of Computer OrganizationComputers are shrinking. Every year there are fewer slots for adapter cards. The goal of the personal computer industry truly is to make the computer as ubiquitous and unobtrusive as possible. At the same time, the computer now contains sufficient technology and raw &horsepower& to run the types of applications and drive the types of tasks that are requiring precision digital input and bandwidth intensive peripherals. Video conferencing on personal computers is today a reality. Surround sound stereo from your personal computer is a standard function. 计算机正在缩小。为适配卡每年都在逐渐减少插槽。个人电 脑产业真正的目标是使电脑尽可能的普及和不唐突。与此同时， 现在的电脑有足够的技术和原“马力”来运行的类应用程序和驱 动器类型的任务，那需要精确的数字输入和带宽密集型外设。今 天在个人电脑上的视频会议已经成为现实。您的个人计算机上的 环绕立体声音是一种标准的功能。 The computer industry is striving to enclose a technology that is expanding to the point that mid-and high-speed digital peripheral devices are required into an ever shrinking footprint. This is where the Universal Serial Bus comes into play. Just put all of the input and output to peripherals outside &the box& and don’t use any slots. Put the intelligence into the devices, rather than into the computer. 计算机行业正在努力附上技术，扩展到中速和高速数字外围 设备需要进入一个不断缩小的空间这个程度。这里是通用串行总 线发挥作用。不使用任何插槽，只是把所有的输入和输出放到外 设之外 “的盒子” ， 并且。 把智力投入到设备中， 而不是电脑中。 Peripherals designers are now freed up to implement solutions that are in &one piece& they don't have to split the functionality of a peripheral between a device and an interface card[2].This is a win for them. As this happens, the internal bus on your computer ceases to bechapter 1 Principles Of Computer Organizationsaturated with traffic and information flowing between these interface cards. This is a win for you；You’ll find that you achieve better overall system performance with this type of configuration. 外设的设计人员实现了一个整体的解决方案，他们不必分割 设备与接口卡之间的外设的功能。对于他们来说这是一个胜利。 因为在这种情况下，在你的电脑上的内部总线终止在这些接口卡 之间交通流和信息流的饱和。 这对于你来说是一个胜利;你会发现 由于这种类型的配置你取得更好的整体系统性能。 Speaker designers are incorporating the functions previously performed by your sound card directly into the speaker. Video-input folks are building video digitizers to plug into the Universal Serial Bus. Even monitor manufacturers are putting Universal Serial Bus interfaces into the backs of their monitors, making the video card obsolete. There are digital joysticks that offer super high resolution. 扬声器的设计者正在合成以前已经实现的功能，即通过由你 的声卡直接进入到扬声器中。视频输入的设计者正在设计可以直 接插入通用串行总线的视频数字化仪。甚至监视器制造商正在把 通用串行总线接口放到他们监视器的后面，使视频卡过时了。有 数字操纵杆，提供超高分辨率。Keywords and Abbreviations:Universal Serial Bus(USB) Video conferencing 通用串行总线 视频会议 myriad digitizers 万，万千 数字化仪Notes：chapter 1 Principles Of Computer Organization[1] The Universal Serial Bus is not considered &fast& when compared to things such as the Fiber Channel serial bus, which clocks in at about 300 million bits per second, or to upcoming bus technologies such as the IEEE 1394 &FireWire& bus to control audio and video sources that are &broadcast quality&. 当 与 象 每 秒 300 百 万 位 的 光 纤 串 行 总 线 和 象 IEEE 1394&FireWire&总线这样用来控制音频和视频资源的未来的总线 技术相比较，不能认为它是高速的总线。 [2] Peripherals designers are now freed up to implement solutions that are in &one piece& they don't have to split the functionality of a peripheral between a device and an interface card. 外设的设计人员实现了一个整体的解决方案，他们不必分割 设备与接口卡之间的外设的功能。Bibliography[1] http://edu.yesky.com. [2] 刘兆毓主编，计算机英语，清华大学出版社，1998。 [3] http://www.educity.cn. [4] http://bbs.itzero.com.chapter 2Operating SystemCHAPTER 2 OPERATING SYSTEMINTRODUCTIONAn operating system (sometimes abbreviated as &OS&) is the program that, after being initially loaded into the computer by a boot program, manages all the other application programs in a computer and performs system services for applications. The application programs make use of the operating system by making requests for services through a defined application program interface. In addition, users can interact directly with the operating system through a user interface such as a command language or a graphical user interface. We also know an Operating System can enables the computer hardware to communicate and operate with the computer software. Without a computer Operating System, a computer would be useless. Operating systems have developed over the past forty years for two main purposes. First, they provide a convenient environment for the development and execution of programs. Second, operating systems attempt to schedule computational activities to ensure good performance of the computing system.chapter 2Operating System2.1 SUMMARY OF OPERATING SYSTEMAn operating system is a program that acts as an intermediary between a user of a computer and the computer hardware. The purpose of an operating system is to provide an environment in which a user can execute programs. The primary goal of an operating system is thus to make the computer system convenient to use. A secondary goal is to use the computer hardware in an efficient manner. 操作系统是一种程序，它工作在用户和计算机硬件之间，起 到中介桥梁作用。操作系统（的目的是）提供给用户一个执行应 用程序的环境。 操作系统的基本目标是