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The Intel 4004 was a 4-bit central processing unit (CPU) released by Intel Corporationmarker in 1971. It was the first commercially available microprocessor, providing a complete CPU on one chip, a feat made possible by the use of then new silicon gate technology allowing the integration of a higher number of transistors and a faster speed than was possible before. The 4004 employed a 10 μm silicon-gate enhancement load pMOS technology and could execute approximately 92,000 instructions per second (that is, a single instruction cycle was 10.8 microseconds).

History and description

Intel D4004
National Semiconductor INS4004.
The 4004 was released on November 15, 1971. Packaged in a 16-pin ceramic dual in-line package, the 4004 was the first computer processor designed and manufactured by chip maker Intelmarker, which had previously made semiconductor memory chips. The chief designers of the chip were Federico Faggin and Ted Hoff of Intel, and Masatoshi Shima of Busicom (later of ZiLOG, founded by Faggin).

Faggin, the sole chip designer among the engineers on the MCS-4 project, was the only one with experience in MOS random logic and circuit design. He also had the crucial knowledge of the new silicon gate process technology with self-aligned gates, which he had created at Fairchild in 1968. At Fairchild, in 1968, Faggin also designed and manufactured the world's first commercial IC using SGT - the Fairchild 3708. As soon as he joined the Intel MOS Department he created a new random design methodology based on silicon gate, and contributed many technology and circuit design inventions that enabled a single chip microprocessor to become a reality for the first time. His methodology set the design style for all the early Intel microprocessors and later for the Zilog’s Z80. He also led the MCS-4 project and was responsible for its successful outcome (1970-1971). Ted Hoff, head of the Application Research Department, contributed only the architectural proposal for Busicom working with Stan Mazor in 1969, then he moved on to other projects. Shima designed the Busicom calculator firmware and assisted Faggin during the first six months of the implementation. The manager of Intel's MOS Design Department was Leslie L. Vadász. At the time of the MCS-4 development Vadasz's attention was completely focused on the mainstream business of semiconductor memories and he left the leadership and the management of the MCS-4 project to Faggin.

The Japanese company Busicom had designed their own special purpose LSI chipset for use in their Busicom 141-PF calculator with integrated printer and commissioned Intel to develop it for production. However, Intel determined it was too complex and would use non-standard packaging and so it was proposed that a new design produced with standard 16-pin DIP packaging and reduced instruction set be developed. This resulted in the 4004, which was part of a family chips, including ROM, DRAM and serial to parallel shift register chips. The 4004 was built of approximately 2,300 transistors and was followed the next year by the first ever 8-bit microprocessor, the 2,500 transistor 8008 (and the 4040, a revised 4004). It was not until the development of the 40-pin 8080 in 1974 that the address and data buses would be separated, giving faster and simpler access to memory.

A popular myth has it that Pioneer 10, the first spacecraft to leave the solar system, used an Intel 4004 microprocessor. According to Dr. Larry Lasher of Ames Research Center, the Pioneer team did evaluate the 4004, but decided it was too new at the time to include in any of the Pioneer projects. The myth was repeated by Federico Faggin himself in a lecture for the Computer History Museummarker in 2006.[15089]

On 15 November 2006, the 35th anniversary of the 4004, Intel celebrated by releasing the chip's schematics, mask works, and user manual.

The 4004 and the MCS-4 family

The 4004 was the world's first commercially available microprocessor - a complete CPU (central processing unit) integrated in a single chip. Before the 4004, CPUs comprised multiple SSI or MSI chips.The 4004 was part of the MCS-4 family of LSI chips that could be used to build digital computers with varying amounts of memory. The other members of the MCS-4 family were memories and input/output circuits, which while not part of a CPU are necessary to implement a complete computer. Specifically:
  • the 4001 was a ROM (read-only memory) with 4 lines of output
  • the 4002 was a RAM (random access memory) with 4 lines of input/output
  • the 4003 was a static shift register to be used for expanding the I/O lines, for example, for keyboard scanning or for controlling a printer

The 4004 included control functions for memory and I/O, which are not normally handled by the microprocessor.

The first commercial product to use a microprocessor was the Busicom calculator 141-PF.

First microprocessor commercially available and sold as a component set

According to Nick Tredennick, a microprocessor designer and expert witness to the Boone/Hyatt patent case :

Technical specifications

  • Maximum clock speed was 740 kHz
  • Separate program and data storage (i.e., a Harvard architecture). Contrary to most Harvard architecture designs, however, which use separate bus, the 4004, with its need to keep pin count down, used a single multiplexed 4-bit bus for transferring:
    • 12-bit addresses
    • 8-bit instructions
    • 4-bit data word
  • Instruction set contained 46 instructions (of which 41 were 8 bits wide and 5 were 16 bits wide)
  • Register set contained 16 registers of 4 bits each
  • Internal subroutine stack 3 levels deep.

Microarchitecture and pinout

Intel 4004 architectural block diagram.

Support chips

  • 4001: 256-byte ROM (256 8-bit program instructions), and one built-in 4-bit I/O port
  • 4002: 40-byte RAM (80 4-bit data words), and one built-in 4-bit output port; the RAM portion of the chip is organized into four "registers" of twenty 4-bit words:
    • 16 data words (used for mantissa digits in the original calculator design)
    • 4 status words (used for exponent digits and signs in the original calculator design)
  • 4003: 10-bit parallel output shift register for scanning keyboards, displays, printers, etc.
  • 4008: 8-bit address latch for access to standard memory chips, and one built-in 4-bit chip select and I/O port
  • 4009: program and I/O access converter to standard memory and I/O chips
  • 4269: keyboard/display interface
  • 4289: memory interface (combined functions of 4008 and 4009)

Naming the first microprocessor

When Federico Faggin designed the MCS-4 family he also christened the chips with distinct names: 4001, 4002, 4003, and 4004, breaking away from the numbering scheme used by Intel at that time which would have required the names 1302, 1105, 1507, and 1202 respectively. Had he followed Intel's number sequence, the idea that the chips were part of a family of components intended to work seamlessly together would have been lost.

Intel's early numbering scheme for integrated circuits contemplated using a four-digit number for each component. The most significant digit position indicated the process technology used, as follows: The number "1" meant P-channel MOS, "2" indicated N-channel MOS, "3" was reserved for bipolar technology, and "5" was used for CMOS technology. No other numbers were used.

The next most significant digit was used to indicate the generic function performed by the component, as follows: "1" was used for RAM, "2" indicated random logic, "3" indicated ROM, "5" meant shift register, "6" and "7" were used for one-time programmable ROM and EPROM respectively. The last two digits of the number were used to indicate the sequential number in the development of the component.

Collectible value

The Intel 4004 is one of the world's most sought-after collectible/antique chips. Of highest value are gold and white 4004s, with so-called 'grey traces' visible on the white ceramic (the original package type). As of 2005, such chips had reached around US$1000 each on eBay. The slightly less valuable white and gold chips without grey traces typically reach $300 to $500. Those chips without a 'date code' underneath are earlier versions, and therefore worth slightly more. More recently however, these vintage ICs have been dropping in value due to their relative abundance as the market is now flooded with surplus stock from sellers looking to cash in on the Intel craze.

The Intel 4004 was designed by physically cutting sheets of Rubylith into thin strips to lay out the circuits to be printed, a process made virtually obsolete by current computer graphic design capabilities.


  • August 14, 1973. Faggin, Federico: Power supply settable bi-stable circuit.
  • June 28, 1974. Hoff, Marcian; Mazor, Stanley; Faggin, Federico: Memory system for multi-chip digital computer.

Historical documents

  • F. Faggin and M.E. Hoff: "Standard parts and custom design merge in four-chip processor kit". Electronics/April 24, 1972, pp. 112-116

  • F. Faggin, M.Shima, M.E. Hoff, Jr., H. Feeney, S. Mazor: "The MCS-4 An LSI micro computer system". IEEE '72 Region Six Conference

  • Federico Faggin, Marcian E. Hoff Jr., Stanley Mazor and Masatoshi Shima. The history of the 4004. IEEE Micro, 16(6):10-20, December 1996. "The 4004 design team tells its story."

  • Live recording of presentations by Ted Hoff and Federico Faggin at the Computer History Museum for the 35th anniversary of the first microprocessor, available also on You Tube (

  • IEEE Solid State Circuits Magazine, Winter 2009 Vol.1 No.1. "The 4004 microprocessor of Faggin, Hoff, Mazor, and Shima".
  • Busicom Calculator Engineering Prototype (Gift of Federico Faggin to the Computer History Museum). The CHM collection catalog shows pictures of the engineering prototype of the Busicom 141-PF desktop calculator. The engineering prototype used the world’s first microprocessor to have ever been produced. This one-of-a-kind prototype was a personal present by Busicom’s president Mr. Yoshio Kojima to Federico Faggin for his successful leadership of the design and development of the 4004 and three other memory and I/O chips (the MCS-4 chipset). After keeping it at home for 25 years, Faggin donated it to the CHM in 1996.


External links

Intel datasheets:

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