Perface
The most beautiful thing we can experience is the mysterious. It is the source of all true art and science.
Albert Einsten, what I believe, 1930
我所经历，最美好的事情是神秘的。它是所有真正艺术和科学的源泉。
艾伯特.爱因思坦，我相信什么，1930.
About This Book 关于本书。
We believe that learning in computer science and engineering should reflect the current state of the field,
as well as introduce the principle that are shaping computer .
我们相信，在计算机科学和工程学习过程中，应该反映该领域的现行状态，还有介绍计算机组成的原理。
We also feel that readers in every specialty of computing need to appreciate the organizational paradigms that determine the capabilities, performance, energy, and ultimately, the success of computer systems.
@specialty /sp'eʃəlti/ 1.(N-count) Someone's specialty is a particular type of work that they do most, or a subject that they know a lot about.某人的specialty是他们做的最多的一种特殊工作类型，或者某一学科，他们懂得更多。
2.(N-count) A specialty of a particular place is a special food or product that is always very good there. 一个特殊地方的Specialty 是当地的一种特殊食物或产品。 @
@appreciate/əpr'i:ʃieit/ (appreciates, appreciating, appreciated) 1.[verb] If you appreciate something, for example a piece of music or good food, you like it because you recognize its good qualities. 如果你appreciate 某事件事情，例如一段音乐或者好的食物, 你喜欢它，因为你认可它的好品质。
In time you will appreciate the beauty and subtlety of this language. 随着时间的推移，你会明白这种语言的美再丽和微妙。（参考google翻译）
2. [verb] vn, v that; If you appreciate a situation or problem, you underatand it and know what it involves. 如果你欣赏一种形势或者问题， 你了解它并且，知道它所涉及的内容。
He appreciates that co-operation with media is part of his professional duties. 他很赞许，与媒体合作是他专业职责中的一部分。
3. [verb] vn, v it if; If you appreciate something that someone has done for you or is going to do for you, you are grateful for it. 如果你欣赏一些事情， 某人已经为你做了，或者打算为你做，你是很感激他。
Peter stood by me when I most needed it, I will always appreciate that... 当我最需要帮助时，彼得站在我的立场，我将永远感激那...
I would appreciate it if you wouldn't mention it. 我将不胜感激，如果你没有是及我。
4. [verb] If something that you own appreciates over a period of time, its value increase. 如果你拥的东西，过了一段时间，它的价值增加。
They don't have any confidence that houses will appreciate in value. 他们没有任何的信心，在价值方面，房子将会被欣赏。 @
@ultimately/ʌltimətli/ 1.[adv] adv with v, adv adj Ultimately means finally, after a long and often complicated series of events.
... a tough but ultimately worthwhile struggle. 一个艰难的，但最终值得斗争。eventually
2. [adv] ADV with cl, You use ultimately to indicate that what you are saying is the most important point in a discussion. 你可以使用“ultimately” 以表明你所说得说是在讨论的最重要的一点。Ultimately, Bismarck's revisionism scarcely affected or damaged British interests at all. 最终，俾斯麦的修正主义几乎没有影响或损害英国的根本利益。 @
Modern computer technology requires professionals of every computing specialty to understand both hardware and software.
现代计算机技术，需要每一个计算机专业领域的计算机专家，理解硬件和软件。
@1. specialty/sp'eʃəlti/ 1. (N-count) Someone 's specialty is a particular type of work that they do most, or a subject that they know a lot about.
某人的specialty 是一种特别类型的工作，他们做的最多，或者是一个学科，他们知道许多。
2. (N-count) A specialty of a particular place is a special food or product that is always very good there.
特别寺方的specialty 是一种特殊的食物或者产品， 通常它是很好的在那儿。 @
@2. professional /prəf'eʃənə/ 1. adj. Professional means relating to a person's work, especially work that require special training.
Professional 意味着与某人的工作相关，特别是那种工作需要特殊的培训。
His professional career started at Liverpool University.他的职业生涯开始于 Liverpool大学。 @
The interaction between hardware and software at a variety of levels also offers a framework for understanding the fundamentals of computing.
在多种级别的硬件与软件交互提供了一个理解计算机基础的框架。
Whether your primary interest is hardware or software, computer science or electrical engineering, the central ideas in computer organization and design are the same.
无论你主要的兴趣是硬件或者软件，计算机科学或者电子工程， 在计算机组织中的中心思想是相同的。
Thus, our emphasis in this book is to show the relationship between hardware and software and to focus on the concepts that are the basis for current computers.
因此，在这本书中，我们的强调点，是去展示硬件与软件之间的关系， 并且聚焦于现代计算机的基本概念。
The recent switch from uniprocessor to multi-core microprocessors confirmed the soundness of this perspective, given since the first edition.
最近，从单处理器到多核微处理器的更新，证实了这一观点的正确性，由于第一版的给出。
@3. confirm/kənfʒ:'m/ (confirms, confirming, confirmed)[verb] If something confirms what you believe, suspect, or fear, that it is definitely true.@
While programmers could ignore the advice and rely on computer architects, compiler writers, and silicon engineers to make their programs run faster or be more energry-efficient without change, that era is over.
然而， 程序员可能忽略了忠告， 或者依赖于计算机架构师、编译作者，和硅工程师去使他们的程序运行更快或者在没有改变的情况下能源利用更高，那个时代已经结束。
@ 4. rely/ri'lai/ v. If you rely on someone or something, you need them and depend on them in order to live or work property.@
@5.era/'iərə/n. 年代；@
@6. silion/s'ilikən/ n. silicon is an element that is found in sand and in minerals such as quartz and granite. Silicon is used to make parts of computers and other electronic equipment.@
For programs run faster, they must become parallel.
如果程序更快地运行，他们必须变成并行的。
@7. parallel/p'ærəlel/ n. If something has a parallel, it is similar to something else, but exists or happens in a different place or at a different time.
If it has no parallel or is without parallel, it is not similar to anything else. @
While the goal of many researchers is to make it possible for programmers to be unaware to the underlying parallel nature of the hardware they are programming, it will take many years to realize this vision.
@8. vision /vi'ʒən/ Your vision of a future situation or society is what you imagine or hope it would be like, if things were very different from the way they are now. @
Our view is that for for at least the next decade, most programmers are going to have to understand the hardware/software interface if they want programs to run efficiently on parallel computers.
我们的观点是那，至少下一个十年，大多数程序员正在准备必须理解硬件或软件接口，如果他们想要程序在并行计算机上高效地运行。
The audience for this book includes those with little experience in assembly language or logic design who need to understand basic computer organization as well as readers with backgrounds in assembly language and/or logic design who want to learn how to design a computer or understand how a system work and why it performs as it does.
适合本书的观众，包括那些毫无汇编语言经验或者逻辑设计， 需要去理解基本的计算机组织；还有在汇编语言和逻辑设计有一定基础的读者，想要学习怎样设计计算机，或者理解一个系统怎样工作，或者它为什么按照指令执行。
@9. audience // the audience at a play, concert, film, or public meeting is the group of people watching or listening to it @
About the other book
Some readers may be familiar with Computer Architecture: A Quantitative Approach, popularly know as Hennessy and Patterson (This book in turn is often called Patterson and Hennessy.)
有些读者可能熟悉计算机体系结构：一种定量方法， 普遍知道的Hennessy和Patterson（这本书又被称作Patterson and Hennessy）
@10. quantitative /kw'ɔntitətiv/ adj. quantitative means relating to different sizes or amount of thing.@
Our motivation in writing the the earlier book was to describe the principles of computer architecture using solid engineering fundamentals and quantitative cost/performance trade offs.
我们在写前面的书的动机是描述计算机体系结构采用扎实的工程基础和量化的成本/性能折衷的原则。
@11.trade-off N. count A trade-off is a situation where you make a compromise between two things, or where you exchange all or part of one thing for another.@
We used an approach that combined example and measurements, based on commercial systems, to create realistic design experiences.
我们使用了一种方法， 结合实例和测量方式，基于商业系统，创造一种现实版的设计经验。
Our goal was to demonstrate that computer architecture could be learned using quantitaive methodologies instead of a descriptive approach.
我们的目标，是使用量化的方法去了解计算机体系结构，而不是一种描述性的方法。
It was intended for the serious computing professional who wanted a detailed understanding of computer.
它是专门打算为了计算机专家准备的，他想要对计算机有一个详细的理解。
A majority of the readers for this book do not plan to become computer architects.
这本书的主要读者，并不准备成为计算机架构师。
The perfomance and energy efficiency of future software systems will be dramatically affected,however, by how well software designers understand the basic hardware techniques at work in a system.
将来软件系统的性能和能量利用率将会受到巨大的影响，无论如何， 通过，良好的软件设计师怎样理解基本的硬件技术在一个系统中。
@12. dramatic /drəm'ætik/ A dramatic change or event happens suddenly and is very noticeale and surprising.@
Thus, compiler writers, operating system designers, database programmers, and most other software engineers need a firm grounding in the principles presented in this book.
因此，编译器的编写者，操作系统的设计者，数据库编程人员，还有大多数的软件工程师，需要一个牢固的基础，对于出现在本书中的原理。
Similarly, hardware designers must understand clearly the effects of their work on software application.
相似的，硬件设计人员必须清楚地理解，在软件应用程序方面，他们工作的影响力。
Thus, we know that this book had to be much more than a subset of the material in Computer Architecture, and the material was extensively revised to match the computer audience.
@13. subset/sʌ'bset/ A subset of a group of things is a smaller number of things that belong together within that group.@
因此，我们知道, 这本书必须有比计算机体系架构部分材料还多，这些材料被扩展到计算机的关注者。
We were so happy with the result that the subsequent editions of Computer Architecture were revised to remove most of the introductory material; hence , there is much less overlap today than with the first editions of books.
在这样的结果下，我们很高兴， 计算机体系架构各版的依次修订，除去了大多数的介绍性材料，因此，今天有很少的重复性内容，比起本书的第一版。
@14. revise /riv'aiz/ (revises, revising, revised)1. If you revise the way you think about something,you adjust your thoughts, usually in order to make than better or more suited to how things are. 如果，你revise 你思想问题的方式， 你适应你的思想，通常，为了使事情更好或者事情怎样做更合适。
He soon came to revise his opinion of the profession.他很快就修改了他的专业性的意见。
2. (verb) v.n If you revise a price, amount, or estimate, you change it to make it more fair, realistic, or accurate.
如果你price 价格、数量、或者估值， 你改变它，使它更公正、现实或者精确。
They realised that some of their prices were higher than their competitors' and revised price according.
他们意识到那， 他们价格中的一些比竟争对手的更高，据此，修订价格。
3.[verb] v n for n, v n;
When you revise an article, a book, a law, or a piece of music, you change it in order to improve it, make it more modern, or make it more suitable for a particular purpose.
当你revise 一片文章、 本本书，一段音乐， 你更改它，使它更现代， 使它更合适对于一个特别的目的。
Three editors handled the work of revising the articles for publication...
三位编缉为了发表，处理正在修订的文章。
The staffs should work together to revise the school curriculum.@
工作人员应该一起修订学校的课程表。
@15. Overlap (overlaps, overlapping, overlapped)
The verb is pronounced /əuvəl'æp/, The noun is pronounced /'əuvəlæp/. 动词发音为/əuvəl'æp/，名词发音为/'əuvəlæp/.
1. [v-recip] v n , v pl-n, pln v, pln v n,
If something overlaps another, or if you overlap them, a part of thing occupies the same area as a part of other thing, you can also say that two things overlap.
如果某件事情overlaps另一件事情，或者如果你overlop 它们， 某件事情的一部分占领了另一件事情的同一部位，你也能够说两件事情overlap.
When the bag is folded flat, the bag botton overlaps one side of the bag.
当这个包被水平fold时，包的底部折叠到包的另一边。
Overlap the slices carefully so here are no gaps.
仔细重叠切片，以至于没有缝隙。
2. [v-recip] v n, v with n, pl-n v. If one idea or activity overlaps another, or overlaps with another, they involve some of the same subjects, people, or periods of time.
如果一个想法或科目overlap另一个，或者用另一个overlap,它们涉及相同的科目，人员，或者时间段。 @
About the Asian Edition
相关亚洲版；
With the consent of the authors, we have developed this Asian Edition of Computer Organization and Design: The Hardware/Software Interface, to better reflect local teaching practice of computer course in Asian classrooms and the development of computer technology in this region.
@region/r'i: dʒən/ (N-count) A region is a large area of land that is different from other areas of land, for example because it is one of the different parts of a country with its own customs and characteristics, or because it has a particular geographical feature.
@一个区域， 是一块大面积的陆地， 不同于陆地的其它区域；例如， 因为它是一个国家不同地方之一，有它自已的风俗习惯，或者因为它有一个特别的地理特点。 @
@consent/kəns'ent/(consents, consenting consented)1. [N-uncount] usu with poss If you give your consent to something, you give someone permission to do it.
如果你给你的consent对于某事，你给某人承诺去做某事。@
the major adjustment of content include:
内容的主要调整包括：
@17. adjustment /ədʒ'ʌstmənt/(adjustments) 1. [N-Conut] oft N to/for/in n An adjustment is a small change that is made to something such as a machine or a way of doing something. adjustment 是一次小小的改动，针对某件事情，例如一台机器，或者做某事的方式。
Investment is up by 5.7% after adjustment for inflation. 投资增长了5.7%, 调整后的通货膨胀。2. [n-count] oft N to n An adjustment is an change in a person's behaviour or thinking. adjustment是一个人的动作和思维的改变。
He will have to make major adjustments to his thinking if he is to survive in office. 他将不得不对于他的思想作出重大的调整，如果他想在办公室生存下去。 @
1. An introduce to the "Th-2 High Performance computing System"(as a demonstration of cluster computing system) to replace Appendix B on digital logic, and a new section on "Networks-on-Chip" as Appendix F.
@cluster /kl'ʌstə/ (clusters, clustering, clustered) 1. (N-count) oft N of n
A cluster of people or things is a small group of them close together. 人或事物的cluster是一小群人紧紧靠在一起。
There is no town here, just a cluster of shops, cabins and motels at the side of highway.在铁路旁边，没有城镇，只有几个商店，小木屋和汽车旅馆。@
针对“th-2高性能计算机系统（展示了一种云计算机系统）”的介结，取代了附录B 数字逻辑，和在附录F中的新章节“Networks-on-chip”.
Both reflect the latest progress in computer technology and can serve as good reference for readers.
在计算机技术里，反映最新的进展，并且，对于读者可以作为很好的参考。
2. Abridgment of some sections of Chapter 2 to better suit the current curriculumns applied in Asian classroom.
@abridgment /əbridʒmənt/n. 节本；缩减；节略；
@19. curriculum /kər'kjuləm/ (curriculums, or curricular/kər'kjulə/)1. [N-count]
A curriculum is all the different courses of study that are taught in a school, collage, or university.
A curriculum 是学习的不同课程，在中学、学院、大学被教的。
Russian is the one compulsory foreign language on the school curriculum. 在学校课程中，俄语是一门复杂的语言。
2. [N-count] usu n N,
A particular curriculum is one particular course of study that is taught in a scchool, college, or university.@
第二章中的几节删节，更适应于在亚洲课堂的现行课程。
With these adjustments listed above, the Asian Edition is enhanced with local features while keeping the main structure and knowledge framework of the original version.
以上所列的这些更改， 亚洲版可以增强伴随着当地的特点， 当保持主体架构和原始版本的知识架框。
Special thanks go to Prof. Zhiying Wang, Prof Chung-ping Chung, Associate Prof. Li Shen and Dr. Sheng Ma, for their contributions to the development of this Asian Edition.
特别感谢王志银教授， 钟仲平教授，副教授李申，马盛博士，他们为了这个亚洲版的出版作出贡献。
Changes for the Fifth Edition
第五版的改变：
We had six major goals for the fifth edtion of Computer Organization and Design:
我们有六个主要的目标：对于计算机的组成与设计第五版；
demonstrate the importance of understanding hardware with a running example;
使用了一个运行实例，展示了理解硬件的重要性。
highlight major themes across the topics using margin icons that are introduced early;
@20.margin/m'a:rdʒin/ (margins) 1. [N-count] with supp A margin is the difference between the amounts, especially the difference in the number of votes or points between the winner and loser in an election or other contest.
A margin 是数量之间的差值， 特别是选票或者点击数量上的差值，在一次选举或者其它竞争中的胜利者和失败者。
3. [N-var] with supp If there is a margin for something in a situation, there is some freedom to choose what to do or decide how to do it.
The money is collected in a straigtforeward way with little margin for error...
这些钱被用简单的方法搜集起来，几乎没有一点错误的余地。
2.[n-count] The margin of a written or printed page is the empty space at the side of the page.
书写或印刷页面的margin 是这一页的空白地方；
She added her comments in the margin. 在页边空白地方，加上了她的注释。
4. [n-count] with supp The margin of place or area is the extreme edge of it . 某地或区域的margin是它的极端边沿。
5. 【n-pl】 with supp To be on the margins of a society, group, or activity means to be among the least important parts of it.
Students have played an important role in the past, but for the mom ent, they are on the margins.
The low coastal plain along the western margin.沿着西部边缘较低的西部平原。@
updated examples to reflect changeover from PC era to PostPc era;
更新实例，反映改变实值从PC 时代到后pc时代；
spread the material on I/O throughout the book rather than isolating it into a single chapter; update the technical content to reflect changes in the industry since the publication of the fourth edition in 2009; and put appendices and optional sections online instead of including a CD to lower costs and to make this edition viable as electronic book.
Before discussing the goals in detail, let's look at the table on page vii.
It shows the hardware and software paths through the material.
Chapters 1,4,5 and 6 are found on both paths, no matter what the experience or the focus.
Chapter 1 discusses the importance of energy and how it motivates the switch from single core to multicore microprocessors and introduces the eight great ideas in architecture.
Chapter 2 likely to review material for hardware-oriented programming, but it is essential reading for the software-oriented, especially for those readers in learning more about compilers and object-oriented programming languages.
Chapter 3 is for readers interested in constructing a datapath or in learning more about floating-point arithmetic.
Some will skip parts of Chapter 3, either because they do not need them or because they offer a review.
However, we introduce the running example of matrix multiply in this chapter, showing how subword parallels offers a fourfold improvement, so do not skip section 3.6 to 3.8.
Chapter 4 explains pipelined processors.
Section 4.1, 4.5, and 4.10 give overviews and 4.12 gives the next performance boost for matrix multiply for those with a software focus.
Those with a hardare focus, however, will find that this chapter presents core material; they may also, depending on their background, want to read Appendix C on logic design first.
The last chapter on multicores, multiprocessors, and clusters, is mostly new content and should be read by everyone.
It was significantly reorganized in this edition to make the flow of ideas more natural and to include much more depth on GPUs, warehouse scale computers, and the hardware-software interface of network interface cards that are key to clusters.
The first of the six goals for this fifth edition was to demonstrate the importance of understanding modern hardware to get good performance and energy efficiency with a concrete example.
As mentioned above, we start with subword parallelism in Chapter 3 to improve matrix multiply by a factor of 4.
We double performance in chapter 4 by unrolling the loop to demonstrate the value of instruction level parallelism.
Chapter 5 doubles performance again by optimizing for caches using blocking.
Finally, Chapter 6 demonstrates a speedup of 14 from 16 processor by using thread-level parallelism.
All four optimizations in total add just 24 lines of C code to our initial matrix multiply example.
The second goal was to help readers separate the forest from the trees by identifying eight great ideas of computer architecture ealy and then pointing out all the places they occur throughout the rest of the book.
We use (hopefully) easy to remember margin iconsand highlight the corresponding word in the text to remind readers of these eight themes.
There are nearly 100 citations in the book.
No chapter has less than seven examples of great ideas, and no idea is cited less than five times.
Performance via parallelism, pipelining, and prediction are the three most popular great ideas, followed closely by Moore's Law.
The processor chapter (4) is the one with the most examples, which is not a surprise since it probably received the most attention from computer architects.
The one great idea found in every chapter is performance via parallelism, which is a pleasant observation gievn the recent emphasis in parallelism, which is a pleasant obsercvation given the recent emphasis in parallesim in the field and in edition of this book.
The third goal was to recognize the generation change in computing from the PC era to PostPc era by this edition with our example and material.
Thus, chapter 1 dives into the guts of a tablet computer rather than a PC, and Chapter 6 describles the computing infrastructure of the cloud.
We also feature the ARM, which is the instruction set of chioce in the personal mobile devices of the PostPC era, as well as the X86 instruction set that dominated the PC Era and (so far) dominates cloud computing.
The fourth goal was to spread the I/O material throughout the book rather than have it in its own chapter, much as we spread parallelism throughout all the chapters in the fourth edition.
Hence, I/O material in this edition can be found in sections 1.4, 4.9, 5.2, 5.5, 5.11 and 6.9.
The thought is that reader (and instructors) are more likely to cover I/O if it's not segreagted to its own chapter.
This is a fast-moving field, and, as is always the case for our new editions, an important goal is to update the technical content.
The running example is the ARM Cortex A8 and Intel Core i7, reflecting our PostPC Era.
Other highlights include an overview the new 64-bit instruction set of ARMv8, tutorial on GPUs that explains their unique terminology, more depth on the warehopuse scale computers that make up the cloud, and a deep dive into 10 Gigabyte Ethernet cards.
To keep the main book short and compatible with electronic books, we placed the optional material as online appendices instead of on a companion CD as in prior editions.
Finally, we updated all the exercises in the book.
最后，我们升级了所有的练习题。
While some elements changed, we have preserved useful book elements from prior editions.
To make the book work better as a reference, we still place definitions of new terms in the margins at their first occurrence.
The book element called "understanding Program Performance" sections helps readers understand the performance of their programs and how to improve it, just as the "Hardware/software Interface" book element helped readers understand the tradeoffs at this interface.