microprocessor

microprocessor, integrated circuit containing the arithmetic, logic, and control circuitry required to interpret and execute instructions from a computer program. When combined with other integrated circuits that provide storage for data and programs, often on a single semiconductor base to form a chip, the microprocessor becomes the heart of a small computer, or microcomputer. Microprocessors are classified by the semiconductor technology of their design (TTL, transistor-transistor logic; CMOS, complementary-metal-oxide semiconductor; or ECL, emitter-coupled logic), by the width of the data format (4-bit, 8-bit, 16-bit, 32-bit, or 64-bit) they process; and by their instruction set (CISC, complex-instruction-set computer, or RISC, reduced-instruction-set computer; see RISC processor). TTL technology is most commonly used, while CMOS is favored for portable computers and other battery-powered devices because of its low power consumption. ECL is used where the need for its greater speed offsets the fact that it consumes the most power. Four-bit devices, while inexpensive, are good only for simple control applications; in general, the wider the data format, the faster and more expensive the device. CISC processors, which have 70 to several hundred instructions, are easier to program than RISC processors, but are slower and more expensive.

Developed during the 1970s, the microprocessor became most visible as the central processor of the personal computer. Microprocessors also play supporting roles within larger computers as smart controllers for graphics displays, storage devices, and high-speed printers. However, the vast majority of microprocessors are used to control everything from consumer appliances to smart weapons. The microprocessor has made possible the inexpensive hand-held electronic calculator, the digital wristwatch, and the electronic game. Microprocessors are used to control consumer electronic devices, such as the programmable microwave oven and videocassette recorder; to regulate gasoline consumption and antilock brakes in automobiles; to monitor alarm systems; and to operate automatic tracking and targeting systems in aircraft, tanks, and missiles and to control radar arrays that track and identify aircraft, among other defense applications.

Bibliography

See A. R. Ismail and V. M. Rooney, Microprocessor Hardware and Software Concepts (1987); I. L. Sayers, A. P. Robson, A. E. Adams, and G. E. Chester, Principles of Microprocessors (1991); M. Slater, A Guide to RISC Microprocessors (1992).

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microprocessor

Miniature electronic device that contains the arithmetic, logic, and control circuitry needed to function as a digital computer's CPU. Microprocessors are integrated circuits that can interpret and execute program instructions as well as handle arithmetic operations. Their development in the late 1970s enabled computer engineers to develop microcomputers. Microprocessors led to “intelligent” terminals, such as bank ATMs and point-of-sale devices, and to automatic control of much industrial instrumentation and hospital equipment, programmable microwave ovens, and electronic games. Many automobiles use microprocessor-controlled ignition and fuel systems.

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A central processing unit (CPU) contained within a single chip. Today, all computer CPUs are microprocessors. The term originated in the 1970s when CPUs up until that time were all comprised of several chips. Thus, when the entire CPU (processor) was miniaturized onto a single chip, the term "micro" processor was coined. Since the turn of the century, the semiconductor manufacturing process has become so sophisticated that not only one, but two or more CPUs, are built on a single chip (see dual core and multicore).

Microprocessor is often abbreviated MPU for "microprocessor unit" or just MP, the latter also spelled with the Greek µ symbol for micro or the letter "u" as an alternate (µP or uP).

They Started as 8-Bit
The first microprocessors were created by Texas Instruments, Intel and a Scottish electronics company. Who was really first has been debated. First-generation 8-bit families were Intel's 8080, Zilog's Z80, Motorola's 6800 and Rockwell's 6502.

Today's Microprocessors Are 32 and 64-Bit
The 32-bit and 64-bit microprocessors found in most of today's workstations and servers are the x86, PowerPC and SPARC lines. More than 200 million of these chips ship inside general-purpose computers each year.

Eight-Bit Lives On
For embedded systems, newer versions of 8- and 16-bit, first-generation microprocessor families are widely used and exceed the desktop computer and server market in volume. Each year, millions of microprocessors and billions of microcontrollers are built into toys, appliances and vehicles. A microcontroller contains a microprocessor, memory, clock and I/O control on a single chip (see microcontroller). See chip and embedded system.

The 386 Microprocessor

No technology is more incredible than the microprocessor. Every second, trillions of switch openings and closings occur all within a thousandth of an inch below the surface. The older 386 chip is shown here because it contains a mere 275,000 transistors, and you can see some slight detail. Contemporary chips contain hundreds of millions of transistors, which at this magnification would show up only as a sea of gray. (Image courtesy of Intel Corporation.)

The First 25 Years of Evolution

In 25 years, the number of transistors on a microprocessor chip grew from a couple thousand to more than five million. By the turn of the century, the number routinely exceeded 100 million on top-of-the-line chips.

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(architecture)

microprocessor - (Or "micro") A computer whose entire CPU is contained on one (or a small number of) integrated circuits. The important characteristics of a microprocessor are the widths of its internal and external address bus and data bus (and instruction), its clock rate and its instruction set. Processors are also often classified as either RISC or CISC. The first commercial microprocessor was the Intel 4004 which appeared in 1971. This was the CPU member of a set of four LSI integrated circuits called the MCS-4, which was originally designed for use in a calculator but was marketed as "programmable controller for logic replacement". The 4004 is referred to as a 4-bit microprocessor since it processed only 4 bits of data at a time. This very short word size is due mainly to the limitations imposed by the maximum integrated circuit density then achievable. As integrated circuit densities increased with the rapid development of integrated circuit manufacturing technology, the power and performance of the microprocessors also increased. This is reflected in the increase in the CPU word size to 4, 8, 16, and by mid-1980s, 32 bits. The smaller microprocessors have relatively simple instruction sets, e.g., no floating point instructions, but they are nevertheless suitable as controllers for a very wide range of applications such as car engines and microwave ovens. The Intel 4004 was followed with, among others the 4040, 8008, 8080, 8086, 80186, 80286, 80386, 486 and Pentium. Other families include the Motorola 6800 and 680x0 families, National Semiconductor 16000 and National Semiconductor 32000, SPARC, ARM, MIPS, Zilog Z8000, PowerPC and the Inmos Transputer family. The larger, more recent microprocessors families have gradually acquired most of the features of large computers. As the microprocessor industry has matured, several families of microprocessors have evolved into de facto industrial standards with multiple manufacturers and numerous "support" chips including RAM, ROM, I/O controllers etc. A single chip microprocessor may include other components such as memory (RAM, ROM, PROM), memory management, caches, floating-point unit, input/output ports and timers. Such devices are also known as microcontrollers. The one-chip microcomputer is in many respects, a landmark development in computer technology because it reduces the computer to a small, inexpensive, and easily replaceable design component. Microcomputers have given rise to a new class of general-purpose machines called personal computers. These are small low cost computers that are designed to sit on an ordinary office desk or to be portable and fuelled the computer boom of the late 1980s. The most widespread example is the also IBM PC, based on microprocessors from Intel Corporation. Apple Computers, Inc. have also produced a range of personal computers, as have several other companies. See also killer micro, minicomputer, CPU Info Center.