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Since there is not yet a universal definition of Computer Systems Architecture(CSA）, interpretations vary. Student confusion increases because commercial terminology can be even more creative!Sometimes CSA appears in the hardware orientation of digital electronics;at other times it takes on the guise of a unified software specification for a family of computers. Rarely is the central importance of network facilities,
both to the computer designer and to the end user, sufficiently acknowledged, even though we are all aware of its growing significance in society. Indeed, more and more computer science graduates become involved in the data communications industry, and would therefore benefit from grounding in this field. Thus an aim of this text is to place networks solidly within CSA.
It is clear that computers and networks require both hardware and software in order to work. But the historical academic separation of the two poses a difficult balancing problem when presenting such a course.
Both are equally important and strongly connected by their enthusiastic supporters. The distinction between hardware and software can be likened to the distant relationship between the formal team player, rigidly posed in front of the goalmouth, and the exciting unpredictability of the World Cup final.
The static photograph of the players only vaguely hints at the limitless possibilities of the dynamic game. With the increasing sophistication of computer hardware, perhaps it is unfortunate that the taking-apart and exploration of old computers is no longer encouraged. The unexpectedly rising prices of electronic components, added to the need to have modern equipment to run the latest games, have resulted, for the moment, in a salesperson's dream. Unexpectedly, this trend, although attracting many more people to use computers, has had an adverse effect on the fundamental level of knowledge among computing undergraduates on entry to university. Although we cannot turn the clock back to the self-build hobbyist days of home computing,
knowledge of the interaction of hardware and software is still useful, if not necessary, for anyone wanting to be fully involved in the professional use of computers.
Curiosity about the computer systems which surround us, the Internet that frustrates us, and the mobile telephone networks that we increasingly rely on should drive us to investigate and question what is happening in the fields of software and electronics. The facilities that will become available to us in the next few years will depend largely on current developments in microelectronics and software design methodology. It is here that we can look for the future.
Throughout this passage we will treat CSA as a study of the interaction of hardware and software which determines the performance of network computer systems. We will also try to show that computers can always be viewed as hierarchical ordered systems which can be broken down into simpler component parts in order to fully understand their operation.
Unlike other areas of study, such as physics or chemistry, complex ideas can always be split into simpler concepts which may then be understood more easily. This progressive decomposition approach not only is useful when studying computers, but can also be invaluable when designing and building new systems.
Although it is widely recognized that computer systems involve both hardware and software, it is still rare for college computer courses to require you to have a comparable understanding in both fields. Perhaps the analogy of only eating half a boiled egg is appropriate-you risk missing out on the yolk. This separation, or specialization, has a number of serious negative results. When teams of developers are separately recruited as hardware engineers or programmers, the danger of an opposing split progressively opening up between the two camps is always present. Professional rivalry can arise through simple misunderstandings due to the different approaches and vocabulary used by hardware and software engineers. Problems, when they inevitably occur, can be blamed on the other camp and then take longer to resolve. Programmers sometimes find that unsuitable equipment has already been specified without consultation, and hardware designers can sit helplessly by as unsuitable software fails to exploit the performance advantages offered by their revolutionary new circuits.
It has been claimed by some business analysts that hardware manufacturing will be of no great commercial consequence. The profit lies in programming:lead the world in the development of systems software!But it is now clear that in such a rapidly changing world, early access to new hardware designs gives the software industry an important marketing lead. The first software products to exploit some new hardware faculty have a clear leadership in the market-place. The neglect of the hardware side of the computing industry has never delivered any long-term advantage. Understanding basic principles and appreciating their application by modem technology within a range of current products is a central aim of this text. Programmers neglect developments in hardware at their peril. The opposite situation, where software is overlooked, can lead to similar failures. Consider the much greater commercial success of the PC since running the Windows operating system and the recent explosion in use of the Internet. Many excellent machines became commercial failures because of their sub-standard software. These well-rehearsed public examples can be added to and confirmed by thousands of private disasters which all underline the need to pursue hardware and software developments in concert. We now recognize that despite their technical superiority, computer systems can fail to win acceptance for many reasons, such as a poorly thought-out user interface, a lack of applications software, or an inappropriate choice of operating system.
Many recent developments have arisen from a simultaneous advance in hardware and software:windowing interfaces are only possible through sophisticated software and powerful graphics cards;network connections are supported by autonomous coprocessors working with complex driver routines;laser printers became universally popular when the xerography print engine was supplemented by the PostScript interpreter.
Many such examples demonstrate the value of keeping abreast of developments in both hardware and software. An increasing difficulty with investigating the interaction of hardware and software is gaining access to the relevant facilities. With large, multi-user mainframe computers it was understandable that the ordinary programmer was denied
access to the hardware and critical software to protect other users. However, with the introduction of Windows NT such security constraints were introduced to single-user personal workstations, making it impossible to access the hardware directly. Only the operating system code has this privilege, while ordinary programs are forced to call“trusted”system routines to read or write to any part of the hardware.
A remarkable empirical law describing the rapid growth of silicon technology was proposed by Gordon Moore, one of the founders of Intel.
His well-known rule, Moore's Law, states that the amount of circuitry(number of transistors)which can be placed on a given chip area approximately doubles every two years. A circuit designed 24 months ago can now be shrunk to fit into an area of half the size. Intel's original 4004 processor involved 2300 transistors, while the Pentium 4 has somewhere of the order of 42 million. The chip area had not increased by a factor of 2000!This capability to progressively shrink the size of electronic circuits could reduce the chip cost, because more circuits are processed on a single slice of silicon, but the technical advance has more often been exploited by enhancing the chip's functionality.
Surprisingly, this law has held true since the early 1970s and is likely to stand well into the 2020s before the size of circuit elements become so small that quantum physics intervenes through Heisenberg's uncertainty principle.
Already the on-chip circuit interconnections are only 0.25 um long and the insulating layers can be as thin as a couple of dozen molecules. However, Moore's Law remains somewhat of a mystery, given that the underlying variables responsible for the trend are as diverse as the ability to maintain ultra-clean factory environments, reduction of international trade barriers, development of increasingly high-resolution technology and the marketing success of games consoles!
Although the split between those concerned with hardware and those concerned with software is now deeply rooted, there are developments which might reverse this trend. As manufacturing techniques allow components to shrink in size, hardware engineers find it increasingly difficult to wire up“breadboard”prototypes because the circuits they are building have grown too complicated.
In any case, the performance of the large-sized components which they can handle easily in a traditional way is not identical to that of the miniature equivalents which will make up the final integrated circuit that is produced.
In the past there was a tendency for trained electronic engineers to migrate towards software, to pick up programming skills and to get involved in systems programming. Will this trend now be reversed?Programmers, software engineers, trained to deal with large systems and complex specifications, may take the opportunity of contributing to the hardware design. This is another example of how hardware and software can come together through the tools and skills demanded by systems developers.
I. Choose the best answer :
1. There is no universal definition of CSA because___________.
A. it's difficult to give one
B. its implications are various
C. its meaning is already clear
D. it is truly an integrated software specification
2. The CSA in the passage is an abbreviation of___________.
A. China Software Association
B. Computer Software Application
C. Computer Systems Architecture
D. Commercial Standards Administration
3. It may be implied in the passage that_____.
A. hardware is more important than software
B. hardware is less important than software
C. hardware is as important as software
D. Hardware is more expensive than software
4. _____deter mine(s)the performance of network computer systems.
A. Hardware
B. Software
C. Neither of them
D. Both of them
5. Computer systems may fail to win acceptance for the following reasons except_____.
A. a lack of applications software
B. poorly thought-out user interfaces
C. the complicated technology
D. an inappropriate choice of operating systems.
6. The ordinary programmers had no access to the hardware and software so as to_____.
A. protect other users
B. use the relevant facilities
C. help the single users out
D. deny programmers privileges
7. What's true about Gordon Moore?
A. He was one of the two founders of Microsoft with another being Bill Gates.
B. He stated that the number of transistors on a given chip area doubles every two years.
C. He was the first one to use transistors in the Intel's original processor.
D. He predicted that the rapid growth of silicon technology was proven incorrect after 2000.
8. The author implies that_____.
A. software development is the most important at present
B. hardware engineers should not migrate toward software
C. software engineers and hardware ones should work independently
D. the cooperation of software engineers and hardware one is a new trend
9. The passage may be taken from_____.
A. a magazine
B. a textbook
C. a computer ad
D. an instruction manual
10. The passage is mainly about_____.
A. a brief history of software and hardware
B. a new trend of present-day computer science
C. a useful piece of software developed by hardware engineers
D. a strange phenomenon that hardware engineers migrate toward software
II. Say the following is true or false
1. There is already a universally accepted definition of CSA now.
2. We are all aware of the central importance of network facilities.
3. Knowledge of both hardware and software is useful for anyone wanting to be professional in using computers.
4. Computers can always be viewed as hierarchical ordered systems that can be broken down into simpler component parts in order to fully understand their operation.
5. College computer courses always require students to have a comparable understanding in both hardware and software.
6. The profit of hardware lies in programming not in hardware manufacturing.
7. As manufacturing techniques allow components to shrink in size, hardware engineers find it easier to work.
8. Surprisingly, Moore's law has held true since the early 1970s and will probably stand well into the 2020s.