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Intel 8080
The Intel 8080 (''"eighty-eighty"'') was the second 8-bit microprocessor designed and manufactured by Intel and was released in April 1974.〔'' Electronic News'' was a weekly trade newspaper. The same advertisement appeared in the May 2, 1974 issue of ''Electronics'' magazine.〕 It was an extended and enhanced variant of the earlier 8008 design, although without binary compatibility. The initial specified clock frequency limit was 2 MHz, and with common instructions using 4, 5, 7, 10, or 11 cycles this meant that it operated at a typical speed of a few hundred thousand instructions per second.
The 8080 required two support chips to function in most applications, the i8224 clock generator/driver and the i8228 bus controller, and it was implemented in NMOS using non-saturated enhancement mode transistors as loads,〔alternatively called ''pull-ups''〕 therefore demanding a +12 V and a −5 V voltage in addition to the main TTL compatible +5 V.
Although earlier microprocessors were used for calculators, cash registers, computer terminals, industrial robots,〔The 8008 (1972) was used for interpolation and control in ASEA's (now ABB) first line of general industrial robots, introduced October 1973.〕 and other applications, the 8080 became one of the first really widespread microprocessors. This was partly due to its simplifying NMOS implementation (making it TTL compatible), but also to its enhanced instruction set (over the 8008〔The enhancements were largely based on customer feedback and Federico Faggin and others listening to minicomputer-oriented professionals about certain problems and lack of features in the 8008 architecture. (Source: 8008 and 8080 oral histories.)〕) and its subsequent role as the original target CPU for CP/M,〔Partly due to its usable instruction set and "sufficiently" minicomputer-like architecture, where the limited but useful 16-bit capabilities and the external, freely relocatable stack was amongst the most important aspects.〕 the first de facto standard personal computer operating system.〔The fact that the Z80 (and to some extent, the 8085) soon took over most of the CP/M market does not reduce this pivotal role of the 8080.〕
The 8080 was successful enough that compatibility at the assembly language level became a design requirement for the 8086 when design for it was started in 1976. This also means that the 8080 indirectly influenced the ubiquitous 32-bit and 64-bit x86 architectures of today.
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抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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