By the late-1960s, designers were striving to integrate the central processing unit (CPU) functions of a computer onto a handful of MOS LSI chips, called microprocessor unit (MPU) chip sets. Building on 8-bit arithmetic logic units (3800/3804) he designed earlier at Fairchild, in 1969 Lee Boysel created the Four-Phase Systems Inc. AL-1 an 8-bit CPU slice that was expandable to 32-bits. In 1970 Steve Geller and Ray Holt of Garrett AiResearch designed the MP944 chip set to implement the F-14A Central Air Data Computer on six metal-gate chips fabricated by AMI.
Intel's first microprocessor, the 4004, was conceived by Ted Hoff and Stanley Mazor. Assisted by Masatoshi Shima, Federico Faggin used his experience in silicon-gate MOS technology (1968 Milestone) to squeeze the 2300 transistors of the 4-bit MPU into a 16-pin package in 1971. Faggin also supervised Hal Feeney's design of the 8-bit 8008 device announced in 1972. Designed for CTC (later Datapoint), prototypes of the 8008 function were also built by Texas Instruments as the TMX1795 but never offered commercially. Second generation 8-bit designs from Intel (8080) and from a team led by Tom Bennett at Motorola (6800) in 1974 established widespread acceptance of the MPU concept. A low-cost variant on the 6800 architecture by MOS Technology (6502) enabled personal computers and games from Apple, Atari, Commodore and others. By the mid-1970s many vendors offered enhanced 8-bit architectures, with Zilog's Z80 being the most enduring. Two 1975 MPUs that presaged important later trends included RCA's CMOS COSMAC 1802 (1963 Milestone) and John Cocke's 801 RISC device at IBM.
Beginning in the mid-1970s, 16-bit MPUs emerged from General Instrument (CP1600), National (PACE), TI (TMS9900), and Zilog (Z8000). Boosted by the PC boom of the 1980s, Intel's 8086/8088 (IBM PC) and Motorola's 68000 (Macintosh) devices enjoyed the widest market success.
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