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1. The Instruction Cycle

  • Instructions are processed under direction of the control unit in step-by-step manner.

  • Each step is referred to as a phase.

  • There are six fundamental phases of the instruction cycle:

    1. fetch instruction (aka pre-fetch)

    2. decode instruction

    3. evaluate address (address generation)

    4. fetch operands (read memory data)

    5. execute (ALU access)

    6. store result (writeback memory data)

  • Instruction cycle:

      Instruction cycle

  • Pentium 4 instruction cycle:

      Pentium 4 instruction cycle

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