When was the first CPU developed?
History of general-purpose CPUs
In the 1960s, the development of electronic calculators, electronic clocks, the Apollo guidance computer, and Minuteman missile, helped make integrated circuits economical and practical. In the late 1960s, the first calculator and clock chips began to show that very small computers might be possible with large-scale integration (LSI). This culminated in the invention of the microprocessor, a single-chip CPU. The Intel 4004, released in 1971, was the first commercial microprocessor. The origins of the 4004 date back to the "Busicom Project", which began at Japanese calculator company Busicom in April 1968, when engineer Masatoshi Shima was tasked with designing a special-purpose LSI chipset, along with his supervisor Tadashi Tanba, for use in the Busicom 141-PF desktop calculator with integrated printer. His initial design consisted of seven LSI chips, including a three-chip CPU. His design included arithmetic units (adders), multiplier units, registers, read-only memory, and a macro-instruction set to control a decimal computer system. Busicom then wanted a general-purpose LSI chipset, for not only desktop calculators, but also other equipment such as a teller machine, cash register and billing machine. Shima thus began work on a general-purpose LSI chipset in late 1968. Sharp engineer Tadashi Sasaki, who also became involved with its development, conceived of a single-chip microprocessor in 1968, when he discussed the concept at a brainstorming meeting that was held in Japan. Sasaki attributes the basic invention to break the calculator chipset into four parts with ROM (4001), RAM (4002), shift registers (4003) and CPU (4004) to an unnamed woman, a software engineering researcher from Nara Women's College, who was present at the meeting. Sasaki then had his first meeting with Robert Noyce from Intel in 1968, and presented the woman's four-division chipset concept to Intel and Busicom.
X86
At various times, companies such as IBM, NEC, AMD, TI, STM, Fujitsu, OKI, Siemens, Cyrix, Intersil, C&T, NexGen, UMC, and DM&P started to design or manufacture x86 processors (CPUs) intended for personal computers as well as embedded systems. Such x86 implementations are seldom simple copies but often employ different internal microarchitectures as well as different solutions at the electronic and physical levels. Quite naturally, early compatible microprocessors were 16-bit, while 32-bit designs were developed much later. For the personal computer market, real quantities started to appear around 1990 with i386 and i486 compatible processors, often named similarly to Intel's original chips. Other companies, which designed or manufactured x86 or x87 processors, include ITT Corporation, National Semiconductor, ULSI System Technology, and Weitek.