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Chapter 1
An Introduction to Architecture and Machines |
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The most important influences on the design of a computing machine or processor are the instruction set (or sets) executed and the technology used in its implementation. In order to understand the machine design process, one must first understand the instruction set and the function of each instruction. |
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The term computer architecture [16] is usually used to describe the instruction set together with major implementation details such as bus structure, storage type, register type, etc. While the instruction set implies many of these implementation details, the implementation is separate from the architecture, since the implementation is the mechanism that executes or interprets the instruction (Figure 1.1). If an instruction specifies 16 generalpurpose registers, most implementations have at least 16 registers. Implementations that have significantly more or fewer than this number are interesting exceptions, which we consider later in this book. Our primary interest in this chapter is to review the concepts and requirements implied by instruction sets, since they form the basis for intelligent machine design. |
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The term architecture includes the instruction set, which yields an interpretable program representation. Multiple implementations of the System 370 instruction set, the VAX [32, 31], the Motorola M680x0, the Intel iAP x86 [58], and the RISC instruction sets (such as SPARC) illustrate the various cost-performance technology tradeoffs possible in creating a machine. |
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One of the longest-lived instruction sets is the IBM mainframe System/360 (S/360), introduced in 1963 [140,141,142,143]. Although over the years it has been relabeled (S/370, S/370 ESA, Enterprise system, and System/390) and extended, the S/360 core instruction set remains unchanged and probably will continue for some time. Over the years, perhaps 100 different machines have implemented this core instruction set, including manufacturers such as IBM (S/370, 30X0 models, Enterprise system, etc.), Amdahl (V series), Hitachi (H series), Fujitsu, and others. For general-purpose usage, the hallmark of a good instruction set is its ability to provide efficient (cost-performance) machine implementations across wide variances in technology (both hardware and software). As well as being long-lived, |
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