The First Microprocessor--The 40th Anniversary of Intel's 4004

Meet the first microprocessor and see what it was used for--from pinball machines to early electronic voting.

4-bit. 2300 transistors. 740 kHz.

On November 15th, 1971–forty years ago this Tuesday–Intel publicly unveiled the world’s first single-chip microprocessor, the 4004. It was a modest start to what would become a grand silicon empire led by Intel. So modest, in fact, that many would quickly forget the 4004 as Intel churned out more powerful chips throughout the rest of the 1970s–the predecessors of the ones inside every current Windows PC and Mac.

Few commercial products used the 4004. Let’s rediscover seven of them, and learn about the chip’s history along the way.

Calculator Brain

In 1970, Japanese calculator manufacturer Busicom commissioned Intel to implement a custom calculator chipset that Busicom had designed. Intel deemed it too complex for production and countered with a four-chip solution that would greatly reduce the proposed calculator’s complexity. Intel’s solution included the world’s first single-chip microprocessor, the 4004, and three other supporting chips, including a chip that stored a mere 40 bytes of RAM.

The 4004 first appeared in the Busicom 141-PF, seen here, during mid-1971. It sold very well in Japan. A contract renegotiation later in the year left Intel free to sell the chipset to others, which it began to do in November.

(Photos: Intel, Dentaku Museum)

Wall Bowling

Pinball and amusement giant Bally plunged headfirst into the microprocessor era when its engineers designed the 4004 into an electronic arcade game called “Bally Alley.”

Up to four players could compete using the 1974 bowling simulator, whose games played out via indicator lamps on a remote display board. The game’s controller box employed a wireless radio transmitter that eliminated the need for unsightly cords between the box and the display, which was especially handy when operators hung the virtual bowling lane on a wall.

(Photos: Bally)

Processing Words

In the mid-1960s, IBM sold an electric typewriter that stored characters on magnetic tape so it could be edited digitally and typed out later, automatically, if desired. In 1972, calculator manufacturer Wang decided to branch out with a similar machine into the relatively new word processing market.

Wang first unveiled the 1220, seen here. It stored text on a pair of cassette tape drives. In 1975, Wang introduced the 1222, which incorporated an Intel 4004 that helped drive a one-line CRT display for paperless editing. To the right, we see an excerpt from that machine’s schematic showing the 4004 in place.

(Photos: Jim Battle, Wang)

Working in Layers

In the 1970s, creating a computer chip started on paper, where draftsmen would draw the design of the chip to create mask layouts. The five layouts seen here represent manufacturing steps for the Intel 4004′s silicon chip.

Each of these designs had to be blown up and traced onto large glass plates covered with Rubylith, an adhesive masking substance that workers painstakingly cut away to form the chip masks. These masks were then optically reduced to create templates that guided the photolithographic process, which etched the designs onto a silicon wafer. The resulting chip contained the sum of all these designs as if they were laid on top of each other.

(Photos: Intel)

Solid-State Pinball

In 1974, Bally commissioned David Nutting Associates to create the first solid-state pinball controller. Up to that point, pinball machines used relays, switches, and other electromechanical components to keep score and determine the flow of the game.

Nutting engineer Jeff Frederiksen chose the Intel 4004 as the basis of his board and retrofitted a Flicker machine as a prototype. Bally executives were flabbergasted at its simplicity and elegance compared to the noisy, clacking relays. Bally passed on the system, however, which left Nutting free to license the tech to Mirco, who produced the first commercial solid-state pinball machine in 1975 (it used a Motorola 6800).

(Photos: Bally, Jay Stafford, Alexis Tzannes)

A Computer That Fits on a Card

As the maker of the world’s first single chip microprocessor, it makes sense that Intel would create the world’s first commercial microcomputer.

The 1972 SIM-4 marked the first appearance of a microprocessor in a computer product, although it wasn’t designed for consumer use. Instead, Intel offered the SIM-4 as a development system to help customers integrate the 4004 into their own custom projects. The single board computer (left) plugged into a development chassis that allowed it to interface with other cards, such as a PROM programmer seen as part of the assembly to the right.

(Photos: David Fansler, Doug Coward)

Computer Voting, 1976 Style

In the 1960s, IBM introduced a vote-couinting machine called the “Votomatic.” The voter would punch holes in a ballot card with a metal stylus to select choices printed on the ballot. Stacks of punched ballots from a precinct would be moved to a central location for scanning by a computer.

In 1976, Compuvote Corporation sought to speed up tabulation by eliminating the need for card transport. It created an electromechanical grid that, when placed under the punch cards, could tally votes electronically. A control system in each booth used an Intel 4004 and 512 bytes of RAM to collect voting information. The system sent votes to a central office over a modem. The solution never saw widespread use.

(Photos: Computerworld, Compuvote Corp.)

Intellec 4 Development System

A year after Intel released the SIM-4, it refined its 4004 development system into the more polished Intellec 4 (1973), seen here. It contained a PROM programming socket on its face and allowed users to step through their 4004 programs for debugging.

The 4004 was so slow, however, that users of the Intellec 4 recall having to wait 30 minutes for assembler software to load so they could start programming.

(Photos: Johanic Peterson)

The Big Debut

While the 4004 had first appeared quietly in Busicom 141-PF earlier in 1971, it wasn’t until November that Intel announced its first microprocessor to the general market. It did so using a carefully placed advertisement in the November 15, 1971 issue of Electronic News, an important trade newspaper for the emerging semiconductor industry.

Here we see the original advertisement, which touts “a micro-programmable computer on a chip!”. It shows large representations of the 4004 along with the three other chips in the MCS-4 chipset (short for “Micro Computer System”) — the 4001, 4002, and 4003. When combined, these chips made a complete microcomputer possible.

(Photo: Intel)

The 4004 Grows Up

Only five months after the launch of the 4004, Intel shipped the 8008, the first 8-bit microprocessor, which began as a custom processor for a Datapoint terminal that Datapoint ultimately declined to use. The 8008 launched a new era of hobbyist microcomputers, such as the Mark-8, which catalyzed the PC industry with an appearance on the cover of Radio-Electronics in 1974. Future Intel chips would follow, each pushing the PC further into the mainstream.

(Photos: Intel, Bryan Blackburn)