The central processing unit (CPU) is the part of a computer that interprets and carries out the instructions contained in the software.

Overview

This CPU uses numerous pins to connect to the motherboard.

Most CPUs divide the tasks of interpreting and carrying out the instructions between:

1. A control unit that directs program flow and
2. One or more execution units that perform operations on data.

Almost always, a CPU includes a collection of registers to hold operands and intermediate results.

When every part of a CPU sits on a single physical integrated circuit, one calls it a microprocessor. Practically all CPUs manufactured today class as microprocessors.

The term "CPU" often refers—imprecisely—to other centrally important parts of a computer, such as caches and input/output controllers, especially when those functions exist on the same microprocessor chip as the CPU. With the arrival of multi-core chips, the term CPU can either mean the physical chip (see the picture) mounted on the motherboard, or it can mean the core within the chip.

Manufacturers of desktop computers often erroneously describe the entire personal computer (the system unit or sometimes white box, including the computer case and the computer hardware it contains) as the CPU. Rather, the CPU, as a functional unit, consists of that part of the computer which actually executes the instructions (add, subtract, shift, fetch, etc.).

A family of CPU designs can class as a CPU architecture.

Types of CPUs

Many processor architectures can also be characterized by their CPU design, like register size. Today most desktop computers and laser printers have 32-bit processors; with 64-bit processors becoming more widespread. Smaller devices like mobile phones, PDAs, or portable video game devices may have 16 or 8-bit processors. Embedded systems such as microwave ovens, calculators, computer keyboards, and infrared remote controls typically have 8-bit or 4-bit processors.

Several major CPU manufacturers have begun to push the idea of using multiple-core processors in personal desktop computers.

Notable CPU architectures

Embedded CPU architectures

• Intel's 8051 architecture

Microcomputer/PC CPU architectures

• Intel's x86 architecture
• Motorola's 6800, 6809, and 68000 architectures
• MOS Technology's 6502 architecture
• Zilog's Z80 architecture
• The AIM Alliance's PowerPC architecture

Workstation/Server CPU architectures

• Sun Microsystems's SPARC architecture
• IBM's POWER architecture
• MIPS Computer Systems Inc.'s MIPS architecture and its instruction set is the vehicle for David A. Patterson and John L. Hennessy Computer Organization and Design ISBN 1-55860-428-6 1998 (2nd. edition)
• HP's PA-RISC architecture
• DEC's Alpha architecture
• The Advanced RISC Machines' (originally Acorn) ARM and StrongARM/XScale architectures
• LEON2 Processor

Mini/MidRange/Mainframe CPU architectures

• IBM's System/360 architecture
• DEC's PDP-11 architecture, and its successor, the VAX architecture
• SuperH's SuperH architecture
• UNIVAC 1100/2200 series architecture (currently supported by Unisys ClearPath IX computers)
• 1750A, the U.S.'s military standard computer.
• AP-101, the space shuttle's computer

Emerging CPU architectures

• AMD's x86-64 architecture (AMD AMD64 and Intel EM64T)
• IBM's Cell architecture (Sony/IBM Cell processor)

Historically important CPUs

• EDSAC- the first practical stored-program computer
• Apollo Guidance Computer, used in the moon flights
• MIPS R4000, the first microprocessor to use a 64-bit datapath.

See also

• addressing mode
• arithmetic and logical unit
• BIOS
• clock rate
• computer bus
• computer engineering
• CPU cooling
• CPU design
• CPU locking
• CPU power consumption
• floating point unit
• front side bus
• instruction pipeline
• instruction set
• microarchitecture
• microcode
• motherboard
• processor
• superscalar
• superpipelined
• wait state

External links

• Tom's Hardware
• AnandTech
• The Overclocker's Club
• CPU-Collection
• Freedom CPU
• Laptop Processors