computer architecture In computer engineering, computer architecture is a description of the structure of a computer system made from component parts. It can sometimes be a high-level description that ignores details of the implementation. At a more detailed level, the ...

, 4-bit

integer An integer is the number zero (), a positive natural number (, , , etc.) or a negative integer with a minus sign ( −1, −2, −3, etc.). The negative numbers are the additive inverses of the corresponding positive numbers. In the languag ...

s, or other

data In the pursuit of knowledge, data (; ) is a collection of discrete Value_(semiotics), values that convey information, describing quantity, qualitative property, quality, fact, statistics, other basic units of meaning, or simply sequences of sy ...

units are those that are 4

bit The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represente ...

s wide. Also, 4-bit

central processing unit A central processing unit (CPU), also called a central processor, main processor or just Processor (computing), processor, is the electronic circuitry that executes Instruction (computing), instructions comprising a computer program. The CPU per ...

(CPU) and arithmetic logic unit (ALU) architectures are those that are based on

register Register or registration may refer to: Arts entertainment, and media Music * Register (music), the relative "height" or range of a note, melody, part, instrument, etc. * ''Register'', a 2017 album by Travis Miller * Registration (organ), th ...

s, or

data bus In computer architecture, a bus (shortened form of the Latin '' omnibus'', and historically also called data highway or databus) is a communication system that transfers data between components inside a computer, or between computers. This e ...

es of that size.

Memory address In computing, a memory address is a reference to a specific memory location used at various levels by software and hardware. Memory addresses are fixed-length sequences of digits conventionally displayed and manipulated as unsigned integers. ...

es (and thus

address bus In computer architecture, a bus (shortened form of the Latin '' omnibus'', and historically also called data highway or databus) is a communication system that transfers data between components inside a computer, or between computers. This e ...

es) for 4-bit CPUs are generally much larger than 4-bit (since only 16 memory locations would be very restrictive), such as 12-bit or more, while they could in theory be 8-bit. A group of four bits is also called a nibble and has 2⁴ = 16 possible values. Some of the first

microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circ ...

s had a 4-bit word length and were developed around 1970. Traditional (non-quantum) 4-bit computers are by now obsolete, while recent quantum computers are 4-bit, but also based on

qubits In quantum computing, a qubit () or quantum bit is a basic unit of quantum information—the quantum version of the classic binary bit physically realized with a two-state device. A qubit is a two-state (or two-level) quantum-mechanical system, ...

, such as the IBM Q Experience. See also: Bit slicing#Bit-sliced quantum computers. The first commercial microprocessor was the binary-coded decimal (BCD-based)

Intel 4004 The Intel 4004 is a 4-bit central processing unit (CPU) released by Intel Corporation in 1971. Sold for US$60, it was the first commercially produced microprocessor, and the first in a long line of Intel CPUs. The 4004 was the first significa ...

, developed for calculator applications in 1971; it had a 4-bit word length, but had 8-bit instructions and 12-bit addresses. It was succeeded by the

Intel 4040 The Intel 4040 microprocessor was the successor to the Intel 4004. It was introduced in 1974. The 4040 employed a 10 μm silicon gate enhancement load PMOS technology, was made up of 3,000 transistors and could execute approximately 62,000 inst ...

. The

Texas Instruments Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globa ...

TMS 1000 The TMS1000 is a family of microcontrollers introduced by Texas Instruments in 1974. It combined a 4-bit central processor unit, read-only memory (ROM), random access memory (RAM), and input/output (I/O) lines as a complete "computer on a chip". ...

(1974) was a 4-bit CPU; it had a

Harvard architecture The Harvard architecture is a computer architecture with separate storage and signal pathways for instructions and data. It contrasts with the von Neumann architecture, where program instructions and data share the same memory and pathways. ...

, with an on-chip instruction ROM, 8-bit-wide instructions and an on-chip data RAM with 4-bit words. The

Rockwell PPS-4 The Rockwell PPS-4, short for "Parallel Processing System, 4-bit", was an early 4-bit microprocessor from Rockwell International, released in late 1972. Although practically unknown today, the PPS series was widely used in calculators, games and to ...

was another early 4-bit processor, introduced in 1972, which had a long lifetime in handheld games and similar roles. It was steadily improved and by 1975 been combined with several support chips to make a one-chip computer. The 4-bit processors were programmed in assembly language or Forth, e.g. "MARC4 Family of 4 bit Forth CPU" (which is now discontinued) because of the extreme size constraint on programs and because common programming languages (for

microcontrollers A microcontroller (MCU for ''microcontroller unit'', often also MC, UC, or μC) is a small computer on a single VLSI integrated circuit (IC) chip. A microcontroller contains one or more CPUs ( processor cores) along with memory and programmabl ...

, 8-bit and larger), such as the C programming language, do not support 4-bit data types (C, and

C++ C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...

, and more languages require that the size of the char data type be at least 8 bits, and that all data types other than bitfields have a size that is a multiple of the character size). The 1970s saw the emergence of 4-bit software applications for mass markets like pocket calculators. During the 1980s 4-bit microprocessor were used in

handheld electronic games Handheld electronic games are very small, portable devices for playing interactive electronic games, often miniaturized versions of video games. The controls, display and speakers are all part of a single unit. Rather than a general-purpose s ...

to keep costs low. In the 1970s and 1980s, a number of research and commercial computers used

bit slicing Bit slicing is a technique for constructing a processor from modules of processors of smaller bit width, for the purpose of increasing the word length; in theory to make an arbitrary ''n''-bit central processing unit (CPU). Each of these com ...

, in which the CPU's arithmetic logic unit (ALU) was built from multiple 4-bit-wide sections, each section including a chip such as an Am2901 or

74181 The 74181 is a 4-bit slice arithmetic logic unit (ALU), implemented as a 7400 series TTL integrated circuit. The first complete ALU on a single chip, it was used as the arithmetic/logic core in the CPUs of many historically significant minicom ...

chip. The

Zilog Z80 The Z80 is an 8-bit microprocessor introduced by Zilog as the startup company's first product. The Z80 was conceived by Federico Faggin in late 1974 and developed by him and his 11 employees starting in early 1975. The first working samples were ...

, although it is an 8-bit microprocessor, has a 4-bit ALU. Although the

Data General Nova The Data General Nova is a series of 16-bit minicomputers released by the American company Data General. The Nova family was very popular in the 1970s and ultimately sold tens of thousands of units. The first model, known simply as "Nova", was ...

is a series of 16-bit minicomputers, the original Nova and the Nova 1200 internally processed numbers 4 bits at a time with a 4-bit ALU, sometimes called "nybble-serial". The

HP Saturn The Saturn family of 4-bit ( datapath) microprocessors was developed by Hewlett-Packard in the 1980s first for the HP-71B handheld computer and then later for various HP calculators (starting with the HP-18C). It succeeded the ''Nut'' family ...

processors, used in many Hewlett-Packard calculators between 1984 and 2003 (including the

HP 48 series The HP 48 is a series of graphing calculators designed and produced by Hewlett-Packard from 1990 until 2003. The series includes the HP 48S, HP 48SX, HP 48G, HP 48GX, and HP 48G+, the G models being expanded and i ...

of scientific calculators) are "4-bit" (or hybrid 64-/4-bit) machines; as the Intel 4004 did, they string multiple 4-bit words together, e.g. to form a 20-bit memory address, and most of the registers are 64 bits wide, storing 16 4-bit digits. In addition, some early calculators such as the 1967 Casio AL-1000, the 1972

Sinclair Executive The Sinclair Executive was the world's first "slimline" pocket calculator, and the first to be produced by Clive Sinclair's company Sinclair Radionics. Introduced in 1972, there were at least two different versions of the Sinclair Executive, ...

, and the aforementioned 1984

had 4-bit

datapath A datapath is a collection of functional units such as arithmetic logic units or multipliers that perform data processing operations, registers, and buses. Along with the control unit it composes the central processing unit (CPU). A larger datap ...

s that accessed their registers 4 bits (one BCD digit) at a time. 4-bit CPUs/microcontrollers are very hard to find at sellers of semiconductors (including manufacturers' websites, since most if not all have discontinued), while can still be found "brand new" on Ebay.

Uses

While 32- and 64-bit processors are more prominent in modern consumer electronics, 4-bit CPUs can be bought online at down to $0.21 unit price for "used" chips (in bulk for 1000 units, or at $0.67 for low volume), while an 8-bit microcontroller can (or could in 2021) be bought for $0.24 for a single one (also obsolete; and a non-obsolete 8-bit CPUs can be bought for $0.30 per unit, for 702 units at $210.60), a fraction of the 4-bit price, and even a single modern 32-bit microcontroller can be bought for $0.24 and ARM-based down to $0.72 in 2022, so it's unclear if 4-bit CPUs are still used for anything else than for replacement parts. For example, one bicycle computer specifies that it uses a "4 bit, 1-chip microcomputer". Other typical uses include coffee makers, infrared remote controls, and security alarms. The processor in Barbie typewriters that can encrypt is a 4-bit microcontroller.

Details

With 4 bits, it is possible to create 16 different values. All single-digit hexadecimal numbers can be written with four bits. Binary-coded decimal is a digital encoding method for numbers using decimal notation, with each decimal digit represented by four bits.

List of 4-bit processors

Alps remote control BHR970001B - NEC D63GS-7525

(first 4-bit microprocessor from 1971, though

Four-Phase Systems Four-Phase Systems was a computer company, founded by Lee Boysel and others, which built one of the earliest computers using semiconductor main memory and MOS LSI logic. The company was incorporated in February 1969 and had moderate commercial ...

AL1 from 1969 is older, discontinued 1981) *

(discontinued 1981) *

(the first high-volume commercial microcontroller, from 1974, after Intel 4004; now discontinued) * Atmel MARC4 core – (discontinued because of Low demand. "Last ship date: 7 March 2015") *

Samsung The Samsung Group (or simply Samsung) ( ko, 삼성 ) is a South Korean multinational manufacturing conglomerate headquartered in Samsung Town, Seoul, South Korea. It comprises numerous affiliated businesses, most of them united under the ...

S3C7 (KS57 Series) 4-bit microcontrollers (RAM: 512 to 5264 nibbles, 6 MHz clock) *

Toshiba , commonly known as Toshiba and stylized as TOSHIBA, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan. Its diversified products and services include power, industrial and social infrastructure systems, ...

TLCS-47 series *

NEC is a Japanese multinational information technology and electronics corporation, headquartered in Minato, Tokyo. The company was known as the Nippon Electric Company, Limited, before rebranding in 1983 as NEC. It provides IT and network soluti ...

μPD75X * NEC μCOM-4 * NEC (now

Renesas is a Japanese semiconductor manufacturer headquartered in Tokyo, Japan, initially incorporated in 2002 as Renesas Technology, the consolidated entity of the semiconductor units of Hitachi and Mitsubishi excluding their dynamic random-access memo ...

) µPD612xA (discontinued), µPD613x, μPD6x and μPD1724x infrared remote control transmitter microcontrollers * EM Microelectronic-Marin EM6600 family, EM6580, EM6682, etc. * Epson S1C63 family *

National Semiconductor National Semiconductor was an American semiconductor manufacturer which specialized in analog devices and subsystems, formerly with headquarters in Santa Clara, California. The company produced power management integrated circuits, display dr ...

"COPS I" and "COPS II" ("

COP400 The COP400 or COP II is a 4-bit microcontroller family introduced in 1977 by National Semiconductor as a follow-on product to their original PMOS COP microcontroller. COP400 family members are complete microcomputers containing internal timing, lo ...

") 4-bit microcontroller families *

MAPS MM570X *

Sharp Sharp or SHARP may refer to: Acronyms * SHARP (helmet ratings) (Safety Helmet Assessment and Rating Programme), a British motorcycle helmet safety rating scheme * Self Help Addiction Recovery Program, a charitable organisation founded in 19 ...

SM590/SM591/SM595 * Sharp SM550/SM551/SM552 * Sharp SM578/SM579 * Sharp SM5E4 * Sharp LU5E4POP * Sharp SM5J5/SM5J6 * Sharp SM530 * Sharp SM531 * Sharp SM500 (ROM 1197×8 bit, RAM 40×4 bit, a divider and 56-segment LCD driver circuit) * Sharp SM5K1 * Sharp SM4A * Sharp SM510 (ROM 2772×8 bit, RAM 128×4 bit, a divider and 132-segment LCD driver circuit) * Sharp SM511/SM512 (ROM 4032×8 bit, RAM 128/142×4 bit, a divider and 136/200-segment LCD driver circuit) * Sharp SM563

References

External links

Saturn CPU
*
Considerations for 4-bit processing
{{CPU technologies Data unit