History of Cpu

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  • Topic: MOS Technology 6502, Microprocessor, Processor register
  • Pages : 2 (830 words )
  • Download(s) : 35
  • Published : July 21, 2010
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The first single chip CPU was the Intel 4004 invented in Nov 1971, a 4-bit processor meant for a calculator. It processed data in 4 bits, but its instructions were 8 bits long. Program and data were separate. In 1972, Texax Instruments followed the Intel 4004/4040 closely with the 4-bit TMS 1000, which was the first microprocessor to include enough RAM, and space for a program ROM, to allow it to operate without multiple external support chips. It also featured an innovative feature to add custom instructions to the CPU. The 8080 was the successor to the 8008 in April 1972. While the 8008 had 14 bit PC and addressing, the 8080 had a 16 bit address bus and an 8 bit data bus. Internally it had seven 8 bit registers, a 16 bit stack pointer to memory which replaced the 8 level internal stack of the 8008, and a 16 bit program counter. It also had several I/O ports - 256 of them, so I/O devices could be hooked up without taking away or interfering with the addressing space, and a signal pin that allowed the stack to occupy a separate bank of memory. Intel updated the design with the 8085 in1976, which added two instructions to enable/disable three added interrupt pins and the serial I/O pins, and simplified hardware by only using +5V power, and adding clock generator and bus controller circuits on-chip.The 8080 was the successor to the 8008 in April 1972. While the 8008 had 14 bit PC and addressing, the 8080 had a 16 bit address bus and an 8 bit data bus. Internally it had seven 8 bit registers, a 16 bit stack pointer to memory which replaced the 8 level internal stack of the 8008, and a 16 bit program counter. It also had several I/O ports - 256 of them, so I/O devices could be hooked up without taking away or interfering with the addressing space, and a signal pin that allowed the stack to occupy a separate bank of memory. Intel updated the design with the 8085 in1976, which added two instructions to enable/disable three added interrupt pins and the serial I/O pins,...
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