Microprocessor is a processor whose elements have been miniaturized into one or a few integrated circuits．It is a semiconductor central processing unit（CPU）and one of the principal components of the microcomputer．The elements of the microprocessor are frequently contained on a single chip or within the same package，but are sometimes distributed over several separate chips．[1] In a microcomputer with a fixed instruction set，the microprocessor consists of the arithmetic-logic unit and the control logic unit．In a microcomputer with a micro programmed instruction set，it contains an additional control-memory unit．[2]
Pentium And Power PC Evolution
    In this section，we provide a brief overview of two computer families：the Intel Pentium and the IBM Power PC．The Pentium represents the results of decades of design effort on complex instruction set computers（CISCs）．It incorporates the sophisticated design principles once found only on mainframes and supercomputers and serves as an excellent example of CISC design．The Power PC is a direct descendant of the first RISC system，the IBM 801，and is one of the most powerful and best-designed RISC-based systems on the market．[3]
    1）The Pentium
    One method of increasing the complexity of an integrated circuit is simply to scale the chip down．[4] For example，if every line etched into the silicon die could be shrunk in half，the same circuit could be built in one -fourth the area．The evolution of dynamic memory chips（DRAMs）follows this rule exactly．The original IBM PC used 16 KB DRAMs．These were soon replaced with 64 Kchips，then 256 KB chips，and now 16 MB，and even 64 MB chips…
The“trick”，of course，is being able to improve processing skills sufficiently to allow this scaling to continue．In 1969，the minimum feature size（the smallest detail that can be etched into a chip）was 10 microns（10×10-6  meter）．By 1997，this had shrunk to 0.25 micron—40 times smaller!
    The Pentium uses a superscalar architecture．This means that the chip’s capabilities go beyond those achieved simply by scaling down its size．In particular，the Pentium is the first microprocessor in the Intel family to support two instruction pipelines，each with its own arithmetic-logic unit，address generation circuitry，and data cache interface．The result is a processor that can actually execute two different instructions simultaneously．
    In 1965，Gordon Moore，one of the founders of Intel，was graphing chip complexity vs. time. He noticed that the number of integrated components doubled every two years．Moore then boldly predicted that this doubling would continue indefinitely．Remarkab1y，his prediction—now referred to as Moore’s law—has held up for more than 30 years．[5]
    2）The Pentium MMX
    In 1996，Intel began delivering versions of the Pentium with multimedia extensions （MMXs）．These processors have three architectural enhancements over non-MMX processors（now renamed Pentium Classic）．
    For general applications，benchmark tests show a 10一20 percent improvement over the Pentium Classic，increasing to nearly 70 percent when multimedia-specific plications are considered．[6] Chips with（internal）click speeds as high as 233 MHz are available．
    Applications of MMX processors include decompression of audio and video files．Indeed，software video players may become a reality．Some vendors are replacing conventional modems and sound cards with MMX-driven software equivalents．
    3）The Pentium Pro
    Perhaps the most striking feature of the Pentium Pro is the package itself．As shown in Fig. 2-1 the Pro consists of two separate silicon dies．The largest is the processor；fabricated with 0.35 micron design rules，it incorporates 5．5 million transistors．The smaller die beside it is a 256 KB level-two cache．Oddly enough，the cache has three times as many transistor，as the processor（16．5 millions），but because of its uniformity，less silicon area is required．[7] Versions of the Pentium Pro with a 512KB，and a 1 MB cache are also available．
    The Pentium Pro retains all of the architectural features of the Pentium that preceded it．That is，internally，all registers are 32 bits，while the external data bus is 64 bits wide．Four additional address lines have been added，allowing 64 GB of physical memory to be accessed．From a software point of view，the Pentium Pro remains 100％ compatible with the previous generation of 80x86 processors．Three new processor instructions have been added，as well as two new floating-point-unit instructions．
    The most touted feature of the Pentium Pro is what Intel calls dynamic execution．This new approach to processing software instructions that reduces idle processor time to an absolute minimum．
    4）The Pentium II
    The newest member of the 80x86 family is the Pentium II．First made available in 1997，it is basically a Pentium Pro with MMX technology．

    The Pentium II is made with 0．25-micron technology，allowing clock speeds of 300 MHz to 450 MHz．System bus frequencies as high as 100 MHz are suonorted．The lower clock speeds will support a 66 MHz system bus frequency．The level-two cache，which operates at half the speed of the processor，stores 512 KB and has its own 64-bit dedicated bus．The level-one cache has been increased from 16 KB in the Pentium Pro to 32 KB in the Pentium II．
    5）Power PC
    In 1975，the 801 minicomputer project at IBM pioneered many of the architecture concepts used in RISC systems．T801，together with the Berkeley RISC I processor，launched the RISC movement．The 801，however，was simply a prototype intended to demonstrate design concepts. The success of the 801 project led IBM to develop a commercial RISC workstation product，the RT PC．The RT PC，introduced in 1986，adapted the architectural concepts of the 801 to an actual product．The RT PC was not a commercial success，and it had many rivals with comparable or better performance．In 1990，IBM produced a third system，which built on the lessons of the 801 and the RT PC．[8] The IBM RISC System /6000 was a RISC-like superscalar machine marketed as a high-performance workstation；shortly after its introduction，IBM began to refer to this as the Power architecture．
    For its next step，IBM entered into an alliance with Motorola，developer of the 68000 series of microprocessors，and Apple，which used the Motorola chip in its Macintosh computers．The result is a series of machines that implement the Power PC architecture． Changes were made to add key missing features and to enable more efficient implementation by eliminating some instructions and relaxing the specification to eliminate some troublesome special case．[9] The resulting Power PC architecture is a superscalar RISC system．
    So far，four member of the Power PC family have been introduced．

    微处理器是一种小型化处理器，其所有元件都在一块或数块集成电路内。它是半导体中央处理器（CPU），是微型计算机的主要部件。微处理器的元件常安装在一个芯片上或在同一组件内，有时也分布在几个芯片上。在具有固定指令集的微型计算机中，微处理器由算术逻辑部件和控制逻辑部件组成。在具有微程序控制的指令集的微型计算机中，它包含附加的控制-存储部件。
    奔腾和威力个人计算机的进展
    这一部分简要介绍一下两个计算机系列：英特尔的奔腾和国际商用机器公司的威力个人计算机。奔腾代表几十年来在复杂指令系统计算机（CISCs）上设计的成果。它综合了以往只有在大型机和超级计算机中才用得上的先进设计原理，成为CISC设计的成功范例。威力电脑是直接从第一个RISC系统即 IBM 801继承下来的，是市场上基于RISC系统的设计得最好、功能最强的系统之一。
    1）奔腾（Pentium）
    增加集成电路集成度的一个方法就是缩小芯片的尺寸。例如，若将刻蚀在硅片压模上的每条线都缩小一半，则同一个电路所占用的面积仅为原来的1/4。动态存储器芯片（DRAM）就是严格按这一规律在发展着。初期的IBM PC使用16KB DRAM芯片，而且很快被64KB芯片所取代；后来采用256KB，现在常用 16MB、甚至64MB……的芯片。
    当然，其窍门仍然是不断改进生产工艺，使尺寸继续缩小。1969年最小“特征”尺寸（指可以光刻到硅片上的最小尺寸）为l0 m，到1997年已达到0. 25 m，缩小了40倍！
    奔腾采用一种超标量体系结构。这表明这种芯片的处理能力超过了单纯减小尺寸所能得到的能力。实际上，奔腾是英特尔系列中第一个支持两条指令流水线的微处理器，每条流水线都有其自己的算术逻辑部件、地址发生电路系统和数据高速缓存接口。这样，一个处理器能同时执行两条不同的指令。
    1965年，戈登•摩尔，英特尔公司创始人之一，绘出了一个芯片集成度与时间的关系图，指出集成电路的元件数每两年翻一番；尔后摩尔大胆预言，这种翻番的趋势将是无期限的。出乎预料的是这一预言（现在都称为摩尔定律）已经持续了30多年。
    2）Pentium MMX
    1996年，英特尔公司开始出售奔腾多媒体扩展版（MMXs）芯片。这些处理器比起非MMX处理器（现在称之为经典奔腾）在结构上有三方面的改进。
    对于一般应用来说，MMX的基准测试结果比经典奔腾改善性能10%~20％，而在特定的多媒体应用中，提高约70％，可用的芯片内部时钟频率高达233MHz。
    MMX处理器的应用包括音像文件的解压缩。实际上，软件视频播放器会成为现实。某些厂商正在用MMX驱动的软件产品取代常规的调制解调器和声卡。
    3）Pentium Pro
    Pentium Pro最显著的特性大概是它的组装本身。图2-1所示的Pentium Pro包括两个单独的硅片。大的一个是处理器，是按0. 35 m工艺设计的，它含有550万个晶体管。旁边一个小的是256KB二级高速缓存。奇怪的是高速缓存所含有的晶体管数为处理器的3倍（165万），这是因为缓存器件具有单一性，所以占用硅面积较小。Pentium Pro还有使用512KB和1MB的高速缓存版本。
    Pentium Pro保持原来奔腾处理器的所有体系结构特性并有所超过。也就是内部寄存器为32位，外部数据总线为64位。另外加了4条地址线，使内存实际编址能力达到64GB。从软件上看，Pentium Pro与前一代80x86处理器100％兼容。另外新增加了3条处理器指令和两条浮点部件指令。
    Pentium Pro最受追捧的特性是英特尔公司称之为动态执行的功能，这一新的处理软件指令的方法将空闲的处理器时间减到最小。
    4）Pentium II
    80x86系列的最新成员是Pentium II。1997年首次上市的Pentium II基本上是采用MMX技术的Pentium Pro。
    Pentium II采用0. 25 m技术，允许的时钟速度为300M~500MHz。系统总线频率高达100MHz。较低的时钟速率也支持66MHz系统总线频率。二级高速缓存工作速度为处理器的一半，容量为512KB，有64位专用总线。一级高速缓存从Pentium Pro的16KB增加为Pentium II的32KB。
    5）威力个人计算机（Power PC）
    1975年，IBM 801小型计算机课题率先提出了许多用于RISC系统的体系结构概念。T801原与贝克利RISC I处理器一起推动了RISC。801只不过是展示设计概念的一个原型，801课题的成功导致了IBM去开发商用的RISC工作站产品RT PC。1986年推出的RT PC将801的体系结构概念用于一个实际产品。RT PC在商业上未获成功，因为它有很多性能相当或更好的竞争对手。1990年IBM在吸取801和RT PC教训的基础上推出了第三个系统。IBM RISC System / 6000是一个RISC类的超标量计算机，并以高性能工作站上市销售。此后不久IBM开始将其称为Power体系结构。
    接下来，IBM与摩托罗拉和苹果公司组成联盟。摩托罗拉是68000微处理器系列的开发者；苹果公司用摩托罗拉芯片生产Macintosh计算机，结果是有一系列实现Power PC体系结构的机器产生。其变化是通过去掉一些指令并放宽规范以消除某些异常情况，以增加一些欠缺的功能并提高实现的效率。最终的Power PC体系结构是一种超标量RISC系统。
    迄今为止威力电脑系列已推出4种产品。