Basics of Computer Architecture
Charles B. Silio · Birkhäuser Boston eBooks · 2005
User-programmable electronic digital computers have progressed through a series of hardware implementations. They began first as cabinets filled with vacuum tubes requiring steel I-beams to support their weight (hence the term “mainframe” to refer to the central processing unit), then as cabinets filled with discrete transistor circuits on cards, then progressed to smaller implementations known as minicomputers (some capable of residing on a desktop), and finally to microprocessors with the components of complete computers residing on only a few integrated circuit chips or even a complete system on only one chip. The term microprocessor derives from the fact that the transistors and interconnecting wires used to implement the processor on an integrated circuit chip are visible only under a microscope. Originally, microprocessors were less capable than their larger brethren, but recently their capabilities and speed exceed those of many of the large mainframes of the 1960s. In this brief introduction to computer architecture, we will specify the instruction set for a small hypothetical computer, discuss the hardware components needed to specify the microarchitecture on which the machine instructions will be interpreted, specify the microprogram [4], [9] for interpreting the original machine instructions, and then specify some more highly encoded microinstructions that can be directly interpreted by the hardware. This will take us from the concept of a complex instruction set computer (CISC), whose instructions are interpreted by a lower set of programs written by a microprogrammer, to a reduced instruction set computer (RISC), whose machine instructions are themselves (for the most part) microinstructions.