First microprocessor

The first commercially-available microprocessor was the Intel 4004, a 4-bit CPU with 2,300 transistors and a clock speed of 740 khz. It was designed by Frederico Faggin, Stanley Mazor, Ted Hoff (at Intel) and Masatoshi Shima (at Busicom) for the Busicom 141-PF calculator. The chip went on sale on 15 November 1971.

The 4004 emerged from a partnership between Intel and Japanese electronics company Busicom, who were developing their own version of the Olivetti Programma 101 (an early electronic calculator). Their engineers came up with an architecture using 12 discrete chips and approached Intel to finalise and manufacture it. Believing Busicom's design to be too complex, Intel's Stanley Mazor and Ted Hoff put together a radical alternative design which incorporated the functions of these 12 chips into just four (ROM, RAM, Shift Register and CPU).

The chip itself was designed by Intel engineer Frederico Faggin and Busicom's Masatoshi Shima. It was capable of between 46,250 and 92,500 instructions per second, meaning it could add two eight-digit numbers in 850 microseconds. A modern desktop CPU, by way of comparison, is capable of around 304,510 MIPS (million instructions per second).

This chip, along with its 8-bit sister, the 8008, established Intel as a player in the world of processor design. Faggin and Shima would join forces again the following year to start work on the 8080, an 8-bit CPU that incorporated many design features from the 4004. The 8080 would go on to power the first wave of relatively low-cost microcomputers and put Intel at the forefront of computer technology.