Brief History of CPU Architecture

For many years, IBM-compatible microprocessors, in a market ruled by Intel, marched along in an orderly fashion: the 286 family, then the 386, then the 486. Each family of processors was more advanced, with a faster array of clock speeds.

The numbering sequence was thrown off in 1993, when Intel introduced its Pentium family to replace the 486 processor, and then again in 1997 when Intel added MMX technology to the Pentium chip to enhance its multimedia capabilities.

Nevertheless, the processor remained in a familiar form: a small, flat chip inserted into a socket on the motherboard, the main circuit board to which all electrical components are attached. Some CPUs fit into different-sized sockets (“Socket 5” and “Socket 7” are two common sizes).

Then came Intel’s Pentium II, which basically merged the capabilities of the home-geared MMX chips and the business-geared Pentium Pros. Instead of a square microprocessor chip, the Pentium II is a larger cartridge, more specifically, a Single Edge Contact (SEC) that consists of the processor and its cache (an area where frequently accessed data and machine instructions are stored), packed into plastic and metal. This cartridge is inserted into a special slot on the motherboard.

TERM TO REMEMBER

Every PC processor has two major, characteristics the generation and the clock speed. A new generation of computer occurs when significant improvements are made to a class of CPUs Generations often are referred to in numbers The oldest PC processors are the 8086 and the 8088, followed by the 286, the 386, and the 486 This numerical progression was interrupted by chip-maker Intel when the company introduced its Pentium processors, the equivalent of the 586. Since then, Intel has introduced the Pentium Pro (686) chip, the Pentium with MMX Technology, and most recently, the Pentium II, which is the fastest of this class of processors. Of course, the other processor makers, led by Cyrix and AMD, continue to release processors with numerical names reminiscent of the Intel line of processors.

Clock speed is the relative measure of the processor’s speed and is measured in megahertz (MHz). Clock speed of a processor is only one factor in a computer’s performance and should never be taken as an absolute measure of a system’s speed, even though some people like to compare clock speed numbers like they compare horsepower in cars. The thing to remember is this: If-and only if all other things are equal-you take two computers of the same generation from the same manufacturer, the one with the higher clock speed will be faster. Clock speed comparisons are only meaningful when you compare two chips of the same generation and manufacturer. For example, you cannot compare the clock speeds of a 486 running at 75MHz and a Pentium running at 150MHz and say the Pentium is twice as fast.