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เนื้อหาย่อ : OBJECTIVES This book is about the structure and function of computers. Its purpose is to present, as clearly and completely as possible, the nature and characteristics of modern-day computer systems. This task is challenging for several reasons. First, there is a tremendous variety of prod- ucts that can rightly claim the name of "computer," from single-chip microprocessors cost- ing a few dollars, to supercomputers costing tens of millions of dollars. Variety is exhibited not only in cost, but also in size, performance, and application. Second, the rapid pace of change that always has characterized computer technology continues with no letup. These changes cover all aspects of computer technology, from the underlying integrated circuit technology used to construct computer components, to the increasing use of parallel orga- nization concepts in combining those components. In spite of the variety and pace of change in the computer field, certain fundamental concepts apply consistently throughout. The application of these concepts depends on the current state of the technology and the price/performance objectives of the designer. The intent of this book is to provide a thorough discussion of the fundamentals of computer orga- nization and architecture and to relate these to contemporary design issues. The subtitle suggests the theme and the approach taken in this book. It always has been important to design computer systems to achieve high performance, but never has this requirement been stronger or more difficult to satisfy than today. All of the basic perfor- mance characteristics of computer systems, including processor speed, memory speed, mem- ory capacity, and interconnection data rates, are increasing rapidly. Moreover, they are increasing at different rates. This makes it difficult to design a balanced system that maxi- mizes the performance and utilization of all elements. Thus, computer design increasingly becomes a game of changing the structure or function in one area to compensate for a per- formance mismatch in another area. We will see this game played out in numerous design decisions throughout the book. A computer system, like any system, consists of an interrelated set of components. The system is best characterized in terms of structure-the way in which components are inter- connected-and function-the operation of the individual components. Furthermore, a com- puter's organization is hierarchical. Each major component can be described further by decomposing it into its major subcomponents and describing their structure and function. For clarity and ease of understanding, this hierarchical organization is described in this book from the top down: Computer system: Major components are processor, memory, I/O. ㆍ Processor: Major components are control unit, registers, ALU, and instruction execution unit. Control Unit: Provides control signals for the operation and coordination of all processor components. Traditionally, a microprogramming implementation has been used, in which major components are control memory, microinstruction sequencing logic, and registers. More recently, microprogramming has been less prominent but remains an important implementation technique.