Central processing unit

The central processing unit (or CPU) is the part of a computer that interprets and carries out the instructions contained in the software. In most CPUs, this task is divided between a control unit that directs program flow and one or more execution units that perform operations on data. Almost always, a collection of registers is included to hold operands and intermediate results.

The term CPU is often used vaguely to include other centrally important parts of a computer such as caches and input/output controllers, especially in computers with modern microprocessor chips that include several of these functions in one physical integrated circuit.

Manufacturers and retailers of desktop computers often erroneously describe the computer case and its contents as the CPU.

A family of CPU designs is often referred to as a CPU architecture.

Notable CPU architectures include:

• Intel's x86 architecture
• Zilog's architecture
• IBM's System/360 architecture
• DEC's PDP-11 architecture, and its successor, the VAX architecture
• Motorola's 68000 architecture
• Sun Microsystems's SPARC architecture
• MIPS Computer Systems Inc.'s MIPS architecture
• HP's PA-RISC architecture
• DEC's Alpha architecture
• The AIM Alliance's PowerPC architecture
• DEC and Acorn ARM's StrongARM 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 new CPU architectures include:

• Intel's Itanium architecture
• AMD's x86-64 architecture

Historically important CPUs have been:

• EDSAC- the first stored-program computer
• Apollo Guidance Computer, used in the moon flights

See also: Arithmetic and Logical Unit, BIOS, computer engineering, CPU design, CPU power consumption, Floating Point Unit, front side bus, microcode, motherboard, CPU unlocking