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.
