The microprocessor's invention marked a pivotal moment in computing history, consolidating the functions of a central processing unit (CPU) onto a single integrated circuit (IC). This breakthrough enabled smaller, cheaper, and more versatile computers, laying the groundwork for personal computing, embedded systems, and the digital revolution.
The Intel 4004 is widely recognized as the first commercially available microprocessor, released on November 15, 1971. It was developed by Intel engineers Marcian "Ted" Hoff, Federico Faggin, and Stanley Mazor, with significant contributions from Japanese engineer Masatoshi Shima from Busicom.
The 4004 was fabricated using silicon gate PMOS technology, measuring about 3mm x 4mm.
While the 4004 is credited as the first microprocessor, Texas Instruments (TI) was closely involved in parallel developments. TI announced the TMS0100 (originally TMS1802NC) on September 17, 1971—two months before the 4004—as a "calculator on a chip." This evolved into the TMS1000 series, released commercially in 1974. The TMS1000 is often considered the first microcontroller (with on-chip RAM and ROM), whereas the 4004 was a pure microprocessor requiring external components. The TMS1000 had around 8,000 transistors, a 4-bit design, and operated at speeds up to 400 kHz. TI's work highlighted the competitive race in miniaturizing computing power.
The 4004 originated from a contract with Japanese calculator manufacturer Busicom. In 1969, Busicom approached Intel to design a set of 12 custom ICs for their high-end printing calculator (model 141-PF). Ted Hoff proposed consolidating the logic into a general-purpose microprocessor, reducing the chip count to four (including the 4004 CPU, ROM, RAM, and I/O). The first functional 4004 was delivered in March 1971. Intel later repurchased the rights from Busicom for $60,000, allowing them to market it broadly. The Busicom 141-PF became the first product to use a microprocessor, demonstrating its practicality for embedded applications.
Beyond calculators, the 4004 found applications in early embedded systems, such as point-of-sale terminals, traffic light controllers, and scientific instruments. Its successor, the Intel 8008 (1972), expanded to 8 bits and was used in terminals and controllers. These chips paved the way for more advanced designs like the 8080 (1974), which powered the Altair 8800—the first successful personal computer kit.
The microprocessor transformed computing by replacing complex, multi-board CPU designs with a single, programmable chip. Key impacts:
The 4004's legacy endures—celebrated in museums and as the foundation of Intel's dominance in processors.