• Created by: SGOzwald
  • Created on: 21-02-18 14:21
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  • CPU
    • Description of the CPU
      • Acts as the brain of the computer
      • Processes all data and instructions that make the systems work
      • Processing power depends on clock speed, number of cores and cache size
      • Architecture refers to the main components of the CPU, how they interact and other parts of the system
        • Main two forms of architecture are Von Neumann and Harvard
    • Main parts
      • The control unit executes program instructions and controls of data inside the CPU (registers, ALU and cache) and outside CPU (memory and output/input devices)
      • The Arithmetic Logic unit completes all calculations
        • Completes simple addition, subtraction, size comparison, multiplication and division
        • Performs logic operations such as AND, OR and NOT, and binary shifts
        • Contains the accumulator which stores the intermediate results of calculations
      • Cache is fast memory within the CPU. Slower than registers but faster than RAM
        • Stores regularly used data so CPU can access the data quickly. CPU will check the cache before it checks ram
        • Have low capacity and are expensive compared to RAM and secondary storage
        • Different levels of cache memory
          • L1 is quickest but has the lowest capacity
          • L2 is slower than L1 has a larger capacity
          • L3 is the slowest but has the greatest capacity
    • Von Neumann architecture
      • Program counter holds the memory address of the instruction of each cycle
      • Accumulator holds intermediate results of calculations in the ALU
      • The memory address register holds the memory address about to be used by the CPU. Applies to data or instructions
      • Memory data register holds the data or instruction
    • Fetch-execute cylce
      • Fetch will copy the memory address from the MAR and will copy the instruction from the MDR. Will increment (increase) the PC to prepare for the next cycle
      • Decode involves the instruction within the MDR is decoded by the control unit. This will prepare for the next step by loading values into the MAR or MDR
      • Execute involves the instruction being performed


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