1.1 System Architecture

1.1 System Architecture

1. Fetch - Decode - Execute

   • Fetches instructions from memory
     • decodes these instruction
       • and then executes them

2. Arithmetic Logic Unit

   • arithemetic operations such as add, subtract, multiply and divide
     • arithmetic operations such as AND, OR and NOT, and the result of 'less than', 'greater than', 'equal to' comparisons
       • binary shift operations (which are used for multiplication or division

3. Control Unit

   • Co-ordinates the activity of the CPU by:
     • fetching then decoding instructions from memory
       • sending out signals to control how data moves around the parts of the CPU and memory, in order to execute these instructions

4. Cache memory

   • the purpose of cache memory is to provide temporary storage that the CPU can access very quickly

5. Registers

   • registers are memory locations within the CPU that hold data temporarily and can be accessed very quickly. They accept, store and transfer data for the CPU

6. Program Counter

   • the program counter keeps track of the memory location for the next instruction

7. Von Neumann Architecture

   • Memory Data Register (MDR)
     • this register is used to store any data fetched from memory or any data that is used to be transferred to and stored in memory
   • Memory address register (MAR)
     • This register stores the location in memory to be used by the MDR
   • Accumulator (ACC)
     • This register either stores the results of any calculations made by the ALU, or stores the value of inputs and outputs to and from the CPU
   • Describes a computer in which the data and instructions are stored in the same area of memory and are indistinguishable from each other.