2 Chapter 1 Fundamentals of Computer Design
This growth rate, combined with the cost advantages of a mass-produced
microprocessor, led to an increasing fraction of the computer business being
based on microprocessors. In addition, two significant changes in the computer
marketplace made it easier than ever before to be commercially successful with a
new architecture. First, the virtual elimination of assembly language program-
ming reduced the need for object-code compatibility. Second, the creation of
standardized, vendor-independent operating systems, such as UNIX and its
clone, Linux, lowered the cost and risk of bringing out a new architecture.
These changes made it possible to successfully develop a new set of architec-
tures, called RISC (Reduced Instruction Set Computer) architectures, in the early
1980s. The RISC-based machines focused the attention of designers on two criti-
cal performance techniques, the exploitation of instruction-level parallelism (ini-
tially through pipelining and later through multiple instruction issue) and the use
of caches (initially in simple forms and later using more sophisticated organiza-
tions and optimizations). The combination of architectural and organizational en-
hancements has led to 20 years of sustained growth in performance at an annual
rate of over 50%. Figure 1.1 shows the effect of this difference in performance
growth rates.
The effect of this dramatic growth rate has been twofold. First, it has signifi-
cantly enhanced the capability available to computer users. For many applica-
tions, the highest performance microprocessors of today outperform the
supercomputer of less than 10 years ago.
Second, this dramatic rate of improvement has led to the dominance of micro-
processor-based computers across the entire range of the computer design. Work-
stations and PCs have emerged as major products in the computer industry.
Minicomputers, which were traditionally made from off-the-shelf logic or from
gate arrays, have been replaced by servers made using microprocessors. Main-
frames have been almost completely replaced with multiprocessors consisting of
small numbers of off-the-shelf microprocessors. Even high-end supercomputers
are being built with collections of microprocessors.
Freedom from compatibility with old designs and the use of microprocessor
technology led to a renaissance in computer design, which emphasized both ar-
chitectural innovation and efficient use of technology improvements. This renais-
sance is responsible for the higher performance growth shown in Figure 1.1—a
rate that is unprecedented in the computer industry. This rate of growth has com-
pounded so that by 2001, the difference between the highest-performance micro-
processors and what would have been obtained by relying solely on technology,
including improved circuit design, is about a factor of fifteen.
In the last few years, the tremendous imporvement in integrated circuit capa-
bility has allowed older less-streamlined architectures, such as the x86 (or IA-32)
architecture, to adopt many of the innovations first pioneered in the RISC de-
signs. As we will see, modern x86 processors basically consist of a front-end that
fetches and decodes x86 instructions and maps them into simple ALU, memory
access, or branch operations that can be executed on a RISC-style pipelined pro-
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普通网友2015-01-06书很好，英文读得累。
GoGoDeveloper2014-11-10《计算机体系结构:量化研究方法(英文版•第5版)》堪称计算机系统结构学科的“圣经”
