Central processing unit

The central processing unit (CPU) is the core component of most electronic devices capable of gaming. CPUs have been used in nearly all computers since the 1970s, including personal computers and video game systems such as consoles and arcade game system boards.

CPUs have typically consisted of a single microprocessor chip since the 1970s. In the 2000s, manufacturers such as Intel and AMD began creating CPUs with multiple microprocessors; these are called "multi-core" CPUs, and are used in both consumer and enterprise environments.

History
In the 1960s, the development of electronic calculators and wristwatches helped make integrated circuit chips economical and practical. In the late 1960s, calculator and wristwatch chips began to show that small computers (compared to large mainframes) might be possible with large-scale integration (LSI). This culminated in the invention of the microprocessor, a single-chip CPU.

The invention of the microprocessor helped in creating a more powerful central processing unit than what was possible in large computers at the time and shrunk it so computers could be smaller. The microprocessor was the major invention that gave birth to the microcomputer, or the personal computer as it is known today.

4-bit
The 4-bit Intel 4004, released in 1971, was the first microprocessor. The origins of the 4004 date back to the 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, ROM, 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 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 Bob Noyce from Intel in 1968, and presented the woman's four-division chipset concept to Intel and Busicom.

Busicom approached the American company Intel for manufacturing help in 1969. Intel, which was more of a memory company back then, had facilities to manufacture the high density silicon gate MOS chip Busicom required. A small Busicom team led by Shima went over to Intel in June 1969, to present Shima's design proposal. Due to Intel lacking logic engineers to understand the logic schematics or circuit engineers to convert them, Intel asked Shima to simplify the logic. Intel wanted a single-chip CPU design, influenced by Sharp's Tadashi Sasaki who presented the concept to Busicom and Intel in 1968. The single-chip microprocessor design was then formulated by Intel's Ted Hoff in 1969, simplifying Shima's initial design down to four chips, including a single-chip CPU. Due to Hoff's formulation lacking key details, Shima came up with his own ideas to find solutions for its implementation. Shima was responsible for the logic design, adding a 10-bit static shift register to make it useful as a printer's buffer and keyboard interface, many improvements in the instruction set, making the RAM organization suitable for a calculator, the memory address information transfer, the key program in an area of performance and program capacity, the functional specification, decimal computer idea, software, desktop calculator logic, real-time I/O control, and data exchange instruction between the accumulator and general purpose register. Hoff and Shima eventually realized the 4-bit microprocessor concept together, with the help of Intel's Stanley Mazor to interpret the ideas of Shima and Hoff. The specifications of the four chips were developed over a period of a few months in 1969, between an Intel team led by Hoff and a Busicom team led by Shima.

In late 1969, Shima returned to Japan. After that, Intel had done no further work on the project until early 1970. Shima returned to Intel in early 1970, and found that no further work had been done on the 4004 since he left, and that Hoff had moved on to other projects. Only a week before Shima had returned to Intel, Italian engineer Federico Faggin had joined Intel and become the project leader. After Shima explained the project to Faggin, they worked together to design the 4004. Thus, the chief designers of the chip were Shima who produced the initial Busicom design and then assisted in the development of the final Intel design, Faggin who created the design methodology and the silicon-based chip design, and Hoff who formulated the architecture before moving on to other projects. The 4004 was first introduced in Japan, as the microprocessor for the Busicom 141-PF calculator, in March 1971, selling 100,000 units. Busicom also used the 4004 for a cash register, billing machine, and teller machine for NCR. In North America, the first public mention of the 4004 was an advertisement in the November 15, 1971 edition of Electronic News.

NEC released the μPD707 and μPD708, a two-chip 4-bit CPU, in 1971. They were followed by NEC's first single-chip microprocessor, the μPD700, in April 1972. It was a prototype for the μCOM-4 (μPD751), released in April 1973, combining the μPD707 and μPD708 into a single microprocessor.

8-bit
The first 8-bit microprocessor was the Intel 8008, released in 1972. It was used for the first microcomputer, the Sord SMP80/08, developed in 1972.

Intel 4004 designers Federico Faggin and Masatoshi Shima went on to design the 8-bit Intel 8080, the first truly general-purpose microprocessor, released in 1974. The Intel 8080 was used for early microcomputers such as the Sord SMP80/x series (1974) and Altair 8800 (1975). The Intel 8080 was also the first microprocessor to be used for a video game, the 1975 arcade game Gun Fight, and was then used for a number of later arcade games, most notably Space Invaders (1978).

Zilog was founded by Federico Faggin in 1974 and joined by Masatoshi Shima in 1975. Faggin and Shima went on to design the Zilog Z80, released in 1976, a successor to their Intel 8080. The Zilog Z80 became the most widely used 8-bit CPU in arcade system boards, and was used in a number of consoles (including the ColecoVision, SG-1000 and Master System) and computers (including the PC-8801, ZX Spectrum, MSX, Sega SC-3000 and SEGA AI Computer).

12-bit
In 1973, Toshiba released the TLCS-12, the first 12-bit microprocessor. 12-bit microprocessors have since been rare, and are not known to have been used for any video game systems.

16-bit
In 1975, Panafacom (a conglomerate of Fujitsu, Fuji Electric and Matsushita) developed the MN1610, the first 16-bit microprocessor. It was used for the Panafacom Lkit-16, the first 16-bit microcomputer, released in 1977.

Zilog Z80 creators Federico Faggin and Masatoshi Shima designed the Zilog Z8000, a 16-bit CPU released in 1979. It was used for the first 16-bit video game, the arcade racing game Pole Position (1982), which used dual Z8000 processors.

The Motorola 68000 was released in 1979. It was a hybrid 16/32-bit CPU. It became the most widely used 16-bit CPU in arcade system boards. It was also used for a number of consoles (such as the Mega Drive and Neo Geo) and computers (such as the Amiga, Atari ST and Sharp X68000).