At one time computers were huge bulky machines which weighed many tons, and operated using old time "vacuum tubes." The invention of the silicon transistor in the early 1940's revolutionized the electronics industry. During the 1970s U.S. companies pioneered new manufacturing techniques called Very Large Scale Integration [VLSI]. It permitted the production of very compact electronic devices. Instead of one transistor, many (in fact, millions on a modern microprocessor) were integrated into a single silicon wafers that could be cheaply mass produced. Commonly referred to as microchips. they led to the development of the microprocessor, a CPU contained on a single microchip sometimes simply called a "computer chip". Pictured below is a highly enlarged photograph (with false coloring) of a Pentium chip manufactured by Intel.
             The microprocessor plugs into a socket which connects it to the motherboard's external bus. A modern microprocessor CPU contains the control unit and arithmetic-logic unit, circuitry to move data between them, a timing device called a "clock" and components to enhance processing efficiencies. Every microprocessor is equipped with special "logic gates" which are special transistorized circuits designed to decode instructions. Usually, microprocessors of a certain "family" are designed to understand a certain set of instruction codes called an instruction set. The computer software must be translated into machine instructions of the appropriate instruction set or they won't run on that computer's microprocessor. The most widely used instruction set used to compile programs written for PCs is Intel corporations's "86x" instruction set.
             The instruction set used by the modern microprocessor may be either a full version called Complex Instruction Set Computing [CISC] or a smaller set called Reduced Instruction Set Computing [RISC]. Intel's 86x instruction set uses CISC. RISC architecture, newer that CISC, has a cons...