Intel 4004

Intel 4004

The 4004 with cover removed (left) and as actually used (right).

The Intel 4004 is generally regarded as the first microprocessor,^[5][6] and cost thousands of dollars.^[7] The first known advertisement for the 4004 is dated November 1971 and appeared in Electronic News.^[8] The project that produced the 4004 originated in 1969, when Busicom, a Japanese calculator manufacturer, asked Intel to build a chipset for high-performance desktop calculators. Busicom's original design called for a programmable chip set consisting of seven different chips. Three of the chips were to make a special-purpose CPU with its program stored in ROM and its data stored in shift register read-write memory. Ted Hoff, the Intel engineer assigned to evaluate the project, believed the Busicom design could be simplified by using dynamic RAM storage for data, rather than shift register memory, and a more traditional general-purpose CPU architecture. Hoff came up with a four–chip architectural proposal: a ROM chip for storing the programs, a dynamic RAM chip for storing data, a simple I/O device and a 4-bit central processing unit (CPU). Although not a chip designer, he felt the CPU could be integrated into a single chip. This chip would later be called the 4004 microprocessor.
The architecture and specifications of the 4004 came from the interaction of Hoff with Stanley Mazor, a software engineer reporting to him, and with Busicom engineer Masatoshi Shima, during 1969. In April 1970, Intel hired Federico Faggin to lead the design of the four-chip set. Faggin, who originally developed the silicon gate technology (SGT) in 1968 at Fairchild Semiconductor^[9] and designed the world’s first commercial integrated circuit using SGT, the Fairchild 3708, had the correct background to lead the project since it was SGT that made it possible to implement a single-chip CPU with the proper speed, power dissipation and cost. Faggin also developed the new methodology for random logic design, based on silicon gate, that made the 4004 possible. Production units of the 4004 were first delivered to Busicom in March 1971 and shipped to other customers in late 1971.