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PREFACE

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 costing 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 has always 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 organization con-
cepts 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 in-
tent 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 has always
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 intercon-
nected, and function—the operation of the individual components. Furthermore, a computer’s
organization is hierarchical.Each major component can be further described 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.
• 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.
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