Intel 4004

The Intel 4004 is a 4-bit central processing unit (CPU) released by Intel Corporation in 1971. Sold for US$60 (,$449.43 in 2023), it was the first commercially produced microprocessor, and the first in a long line of Intel CPUs. The 4004 was the first significant example of large scale integration, showcasing the superiority of the MOS silicon gate technology (SGT). Compared to the incumbent technology, the SGT integrated on the same chip area twice the number of transistors with five times the operating speed. This step-function increase in performance made possible a single-chip CPU, replacing the existing multi-chip CPUs. The innovative 4004 chip design served as a model on how to use the SGT for complex logic and memory circuits, thus accelerating the adoption of the SGT by the world’s semiconductor industry. The developer of the original SGT at Fairchild was Federico Faggin who designed the first commercial integrated circuit (IC) that used the new technology, proving its superiority for analog/digital applications (Fairchild 3708 in 1968). He later used the SGT at Intel to obtain the unprecedented integration necessary to make the 4004. The project traces its history to 1969, when Busicom Corp. approached Intel to design a family of seven chips for an electronic calculator, three of which constituted a CPU specialized for making different calculating machines. The CPU was based on data stored on shift-registers and instructions stored on ROM (read only memory). The complexity of the three-chip CPU logic design led Marcian Hoff to propose a more conventional CPU architecture based on data stored on RAM (random access memory). This architecture was much simpler and more general-purpose and could potentially be integrated into a single chip, thus reducing the cost and improving the speed. Design began in April 1970 under the direction of Faggin aided by Masatoshi Shima who contributed to the architecture and later to the logic design.