8-bit
Encyclopedia
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 computer
s and game consoles of the '70s and '80s. Many 8-bit CPUs or microcontroller
s 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.
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):
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
was the Intel 8080
Intel 8080
The Intel 8080 was the second 8-bit microprocessor designed and manufactured by Intel and was released in April 1974. It was an extended and enhanced variant of the earlier 8008 design, although without binary compatibility...
, being used in many hobbyist computers of the late 1970s and early 1980s, often running the CP/M
CP/M
CP/M was a mass-market operating system created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc...
operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
. The Zilog Z80
Zilog Z80
The Zilog Z80 is an 8-bit microprocessor designed by Zilog and sold from July 1976 onwards. It was widely used both in desktop and embedded computer designs as well as for military purposes...
(compatible with the 8080) and the Motorola 6800
Motorola 6800
The 6800 was an 8-bit microprocessor designed and first manufactured by Motorola in 1974. The MC6800 microprocessor was part of the M6800 Microcomputer System that also included serial and parallel interface ICs, RAM, ROM and other support chips...
were also used in similar computers. The Z80 and the MOS Technology 6502
MOS Technology 6502
The MOS Technology 6502 is an 8-bit microprocessor that was designed by Chuck Peddle and Bill Mensch for MOS Technology in 1975. When it was introduced, it was the least expensive full-featured microprocessor on the market by a considerable margin, costing less than one-sixth the price of...
8-bit CPUs were widely used in home computer
Home computer
Home computers were a class of microcomputers entering the market in 1977, and becoming increasingly common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a single nontechnical user...
s and game consoles of the '70s and '80s. Many 8-bit CPUs or microcontroller
Microcontroller
A microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...
s 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
4-bit
The Intel 4004, the world's first commercially available single-chip microprocessor, was a 4-bit CPU. The F-14 Tomcat's Central Air Data Computer was created a year before the 4004, but its existence was classified by the United States Navy until 1997...
word length and were developed around 1970. The first commercial microprocessor was the BCD-based Intel 4004
Intel 4004
The Intel 4004 was a 4-bit central processing unit released by Intel Corporation in 1971. It was the first complete CPU on one chip, and also the first commercially available microprocessor...
(1971), developed for calculator applications. The first commercial 8-bit processor was the Intel 8008
Intel 8008
The Intel 8008 was an early byte-oriented microprocessor designed and manufactured by Intel and introduced in April 1972. It was an 8-bit CPU with an external 14-bit address bus that could address 16KB of memory...
(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-bitOctet (computing)
An octet is a unit of digital information in computing and telecommunications that consists of eight bits. The term is often used when the term byte might be ambiguous, as there is no standard for the size of the byte.-Overview:...
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
16-bit
-16-bit architecture:The HP BPC, introduced in 1975, was the world's first 16-bit microprocessor. Prominent 16-bit processors include the PDP-11, Intel 8086, Intel 80286 and the WDC 65C816. The Intel 8088 was program-compatible with the Intel 8086, and was 16-bit in that its registers were 16...
), due to practical and economical considerations. This implies a direct address space
Address space
In computing, an address space defines a range of discrete addresses, each of which may correspond to a network host, peripheral device, disk sector, a memory cell or other logical or physical entity.- Overview :...
of only 64 KiB
Kibibyte
The kibibyte is a multiple of the unit byte for quantities of digital information. The binary prefix kibi means 1024; therefore, 1 kibibyte is . The unit symbol for the kibibyte is KiB. The unit was established by the International Electrotechnical Commission in 1999 and has been accepted for use...
on most 8-bit processors.
Early and/or popular 8-bit processors (incomplete):
- Intel 8008Intel 8008The Intel 8008 was an early byte-oriented microprocessor designed and manufactured by Intel and introduced in April 1972. It was an 8-bit CPU with an external 14-bit address bus that could address 16KB of memory...
(1972 Datapoint 2200Datapoint 2200The Datapoint 2200 was a mass-produced programmable terminal, designed by Phil Ray and Gus Roche, announced by Computer Terminal Corporation in June, 1970...
compatible) - Intel 8080Intel 8080The Intel 8080 was the second 8-bit microprocessor designed and manufactured by Intel and was released in April 1974. It was an extended and enhanced variant of the earlier 8008 design, although without binary compatibility...
(1974 8008 source compatible) - Motorola 6800Motorola 6800The 6800 was an 8-bit microprocessor designed and first manufactured by Motorola in 1974. The MC6800 microprocessor was part of the M6800 Microcomputer System that also included serial and parallel interface ICs, RAM, ROM and other support chips...
(1974) - MOS Technology 6502MOS Technology 6502The MOS Technology 6502 is an 8-bit microprocessor that was designed by Chuck Peddle and Bill Mensch for MOS Technology in 1975. When it was introduced, it was the least expensive full-featured microprocessor on the market by a considerable margin, costing less than one-sixth the price of...
(1975 similar to 6800, but incompatible) - Zilog Z80Zilog Z80The Zilog Z80 is an 8-bit microprocessor designed by Zilog and sold from July 1976 onwards. It was widely used both in desktop and embedded computer designs as well as for military purposes...
(1976 8080 binary compatible) - Intel 8085Intel 8085The Intel 8085 is an 8-bit microprocessor introduced by Intel in 1977. It was binary-compatible with the more-famous Intel 8080 but required less supporting hardware, thus allowing simpler and less expensive microcomputer systems to be built....
(1977 8080 binary compatible) - Zilog Z8Zilog Z8The Zilog Z8 is a microcontroller architecture, originally introduced in 1979, which today also includes the eZ8 Encore!, eZ8 Encore! XP, and eZ8 Encore! MC families....
(1978 Harvard architecture microcontroller) - Motorola 6809Motorola 6809The Motorola 6809 is an 8-bit microprocessor CPU from Motorola, designed by Terry Ritter and Joel Boney and introduced 1978...
(1978 partially 6800 compatible) - Intel 8051Intel 8051The Intel MCS-51 is a Harvard architecture, single chip microcontroller series which was developed by Intel in 1980 for use in embedded systems. Intel's original versions were popular in the 1980s and early 1990s. While Intel no longer manufactures the MCS-51, binary compatible derivatives remain...
(1980 Harvard architecture microcontroller) - Zilog Z180Zilog Z180The Zilog Z180 8-bit processor is a successor of the Z80 CPU. It is compatible with the large base of software written for the Z80. The Z180 family adds higher performance and integrated peripheral functions like clock generator, 16 bit counters/timers, interrupt controller, wait-state generators,...
(1985 Z80 binary compatible) - Zilog eZ80Zilog eZ80The Zilog eZ80 is an 8-bit microprocessor which is essentially an updated version of the company's earlier Z80 8-bit microprocessor.The eZ80 is binary compatible with the Z80 and Z180, but almost four times as fast as the original Z80 chip at the same clock frequency...
(1999/2001 Z80 binary compatible) - Motorola 6803
- Freescale 68HC08Freescale 68HC08The 68HC08 is a broad family of 8-bit microcontrollers from Freescale Semiconductor .HC08's are fully code-compatible with their predecessors, the Motorola 68HC05. Like all Motorola processors that share lineage from the 6800, they use the von Neumann architecture as well as memory-mapped I/O...
- Freescale 68HC11Freescale 68HC11The 68HC11 is an 8-bit microcontroller family introduced by Motorola in 1985. Now produced by Freescale Semiconductor, it descended from the Motorola 6800 microprocessor. It is a CISC microcontroller...
- RCA 1802RCA 1802The RCA CDP1802, also known as the COSMAC , is an 8-bit CMOS microprocessor introduced by RCA in early 1976. It is being by Intersil Corporation as a high-reliability microprocessor...
- Hudson Soft HuC6280Hudson Soft HuC6280The HuC6280 8-bit microprocessor is Japanese company Hudson Soft's improved version of the WDC 65C02 CPU. The most notable product using the HuC6280 is NEC's TurboGrafx 16 video game console.-Description:...
- PIC microcontrollerPIC microcontrollerPIC is a family of Harvard architecture microcontrollers made by Microchip Technology, derived from the PIC1650 originally developed by General Instrument's Microelectronics Division...
- Atmel AVRAtmel AVRThe AVR is a modified Harvard architecture 8-bit RISC single chip microcontroller which was developed by Atmel in 1996. The AVR was one of the first microcontroller families to use on-chip flash memory for program storage, as opposed to one-time programmable ROM, EPROM, or EEPROM used by other...
family microcontrollers - NEC 78K0 series * Infineon XC800 familyXC800 familyThe Infineon XC800 Family is an 8-bit Microcontroller family, first introduced in 2005 , with a dual cycle optimized 8051 "E-Warp" Core. The XC800 family is divided in to two categories, the A-Family for Automotive and the I-Family for Industrial & Multi Market applications.-Industrial and...
microcontrollers
See also
- History of video game consoles (third generation)History of video game consoles (third generation)In the history of computer and video games, the third generation began on July 15, 1983, with the Japanese release of both the Nintendo Family Computer and Sega SG-1000...
- VasmVasmvasm is a free assembler supporting various CPUs and many different output formats.CPUs officially supported by vasm include M680x0 family, ColdFire family, 80x86 family, PowerPC, ARM family, Z80 family, C16x/ST10, 6502 etc. Vasm supports Standard MIT , Motorola/Freescale 68k and Old 8-bit style...
, a free assembler