4-bit

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In computer architecture, 4-bit integers, memory addresses, or other data units are those that are at most 4 bits wide. Also, 4-bit CPU and ALU architectures are those that are based on registers, address buses, or data buses of that size.

The first microprocessors had a 4-bit word length and were developed around 1970. The first commercial microprocessor was the binary coded decimal (BCD-based) Intel 4004, developed for calculator applications in 1971; it had a 4-bit word length, but had 8-bit instructions and 12-bit addresses.

Details [edit]

The Intel 4004, the world's first commercially available single-chip microprocessor, was a BCD-based 4-bit CPU. The F-14 Tomcat's Central Air Data Computer (or F14 CADC) was created a year before the 4004, but its existence was classified by the United States Navy until 1997. Also, the Saturn processors, used in calculators such as the commonly used HP-48 scientific calculator, are basically 4-bit machines, although they string multiple 4-bit words together, e.g. to form a 20-bit memory address.

The 1970s saw the emergence of 4-bit software applications for mass markets like pocket calculators.

With 4 bits, it is possible to create 16 different values. All single digit hexadecimal numbers can be written with 4 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 [edit]

This section requires expansion. (May 2008)

• Intel 4004
• Intel 4040
• Atmel MARC4 core ^[1] - Mature.
• Toshiba TLCS-47 series
• HP Saturn (microprocessor)
• NEC μPD75X
• NEC (now Renesas) µPD612xA (discontinued), µPD613x, μPD6x^[2][3] and μPD1724x^[4] infrared remote control transmitter microcontrollers^[5][6]
• TMS1000
• EM Microelectronics EM6600 family, EM6580
• Epson S1C63 family

See also [edit]

• GMC-4

References [edit]

External links [edit]

• Saturn CPU
• [1]
• Considerations for 4-bit processing

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