8-bit

8-bit
Processors
1-bit 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
8-bit 16-bit 32-bit 64-bit
Data Sizes
bit   nibble   octet   byte
halfword   word   dword   qword
IEEE floating-point standard
Single precision floating-point format (32-bit)  Double precision floating-point format (64-bit)  Quadruple precision floating-point format (128-bit)

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 are the norm.

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.

Important 8-bit CPUs

Eight-bit CPUs use an 8-bit data bus and can therefore access 8 bits of data in a single machine instruction. The address bus is typically a double octet wide (i.e. 16-bit), due to practical and economical considerations. This implies a direct address space of only 64 KiB on most 8-bit processors.

Early and/or popular 8-bit processors (incomplete):

See also



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