Central processing unit
The central processing unit (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 when those functions are on the same microprocessor chip as the CPU.
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, is that part of the computer which actually executes the instructions (add, subtract, shift, fetch, etc.).
A family of CPU designs is often referred to as a CPU architecture.
Notable CPU architectures include:
- Intel's x86 architecture
- Intel's 8051 architecture
- MOS Technology's 6502 architecture
- Zilog's z80 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
- The Advanced RISC Machines (originally Acorn) ARM and StrongARM/XScale architectures
- 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:
Historically important CPUs have been:
- EDSAC- the first practical stored-program computer
- Apollo Guidance Computer, used in the moon flights
Types of CPUs
The above processor architectures could also be characterized by their CPU design like register size. Today most desktop computers and laser printers have 32-bit processors; 64-bit processors are being phased in. 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.
- arithmetic and logical unit
- clock rate
- computer bus
- computer engineering
- CPU cooling
- CPU design
- CPU locking
- CPU power consumption
- floating point unit
- front side bus
- instruction pipeline
- wait state