This article is about computer architecture. For other uses, see 8-bit (disambiguation). "IA-8" redirects here. For the former congressional district, see Iowa's 8th congressional district. This article does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (October 2009) Processors 4-bit 8-bit 12-bit 16-bit 18-bit 24-bit 31-bit 32-bit 36-bit 48-bit 60-bit 64-bit 128-bit Applications 16-bit 32-bit 64-bit Data Sizes nibble   octet   byte   word   dword   qword

In computer architecture, 8-bit integers, memory addresses, or other data units are those that are at most 8 bits (1 octet) wide. Also, 8-bit CPU and ALU architectures are those that are based on registers, address buses, or data buses of that size. 8-bit is also a term given to a generation of computers in which 8-bit processors were the norm. Eight-bit CPUs normally use an 8-bit data bus and a 16-bit address bus which means that their address space is limited to 64 KiB. This is not a "natural law", however, so there are exceptions.

The first widely adopted 8-bit microprocessor was the Intel 8080, being used in many hobbyist computers of the late 1970s and early 1980s, often running the CP/M operating system. The Zilog Z80 (compatible with the 8080) and the Motorola 6800 were also used in similar computers. The Z80 and the MOS Technology 6502 8-bit CPUs were widely used in home computers and game consoles of the '70s and '80s. Many 8-bit CPUs or microcontrollers are the basis of today's ubiquitous embedded systems.

There are 28 (256) possible values for 8 bits. The first microprocessors had a 4-bit word length and were developed around 1970. The first commercial microprocessor was the BCD-based Intel 4004 (1971), developed for calculator applications. The first commercial 8-bit processor was the Intel 8008 (1972) which was originally intended for intelligent terminals. Most competitors to Intel started off with such character oriented 8-bit microprocessors. Modernized variants of these 8-bit machines are still one of the most common types of processor in embedded systems. List of 8-bit CPUs

A CPU can be classified on the basis of the data it can access in a single operation. An 8-bit processor can access 8 bits of data in a single operation, as opposed to a 16-bit processor, which can access 16 bits of data in a single operation. 8 Bits Examples of 8-bit processors (very incomplete): Freescale Freescale 68HC08 Freescale 68HC11 Intel Intel 8008 Intel 8080 (8008 source compatible) Intel 8085 (8080 binary compatible) Intel 8051 (Harvard architecture) RCA RCA 1802 Zilog Zilog Z80 (8080 binary compatible) Zilog Z180 (Z80 binary compatible) Zilog Z8 Zilog eZ80 (Z80 binary compatible) Motorola Motorola 6800 Motorola 6803 Motorola 6809 (partially 6800 compatible) MOS Technology MOS Technology 6502 PIC microcontroller Microchip PIC10 Microchip PIC12 Microchip PIC16 Microchip PIC18 Others Atmel AVR family microcontrollers NEC 78K0 series microcontrollers See also History of video game consoles (third generation) Vasm, a free assembler

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