1 - Computer Abstractions and Technology

Abstract

This chapter focuses on the basic ideas and definitions, the major components of software and hardware, and integrated circuits, the technology that fuels the computer revolution. Both hardware and software designers construct computer systems in hierarchical layers, with each lower layer hiding details from the level above. This principle of abstraction is fundamental to understanding today's computer systems, but it does not mean that designers can limit themselves to knowing a single technology. The most important example of abstraction is the interface between hardware and low-level software, called the instruction set architecture. Maintaining the instruction set architecture as a constant enables many implementations of that architecture—varying in cost and performance—to run identical software. On the downside, the architecture may preclude introducing innovations that require the interface to change. Equal in importance to an understanding of integrated circuit technology is an understanding of the expected rates of technological change. One example of this relationship is the dynamic random access memory (DRAM) tradition of a fourfold capacity increase every three years. While silicon fuels the rapid advance of hardware, new ideas in the organization of computers have multiplied price/performance. Two of the key ideas are exploiting parallelism in the processor, typically via pipelining, and exploiting locality of accesses to a memory hierarchy, typically via caches.