von-neumann-and-harvard-architecture

Von Neumann & Harvard Architecture

What is computer architecture?

• A computer architecture describes how it uses the components and instructions to make the computer function

• There are 2 common types of computer architecture:

  • Von Neumann architecture

  • Harvard architecture

Von Neumann Architecture

Layout of Von Neumann Architecture

• Von Neumann’s architecture includes:

  • Control Unit (CU)

    • The control unit controls the operation of the processor and its components

    • It retrieves instructions stored in memory, decodes or interprets them, and then executes them

    • The CU generates timing signals and controls the other units of the computer

  • Arithmetic Logic Unit (ALU)

    • The ALU carries out all the arithmetic and logic operations in the computer such as:

      • Addition

      • Subtraction

      • Multiplication

      • Division

      • Comparisons, etc.

  • Special registers within the CPU

  • A single set of buses to connect the CPU to memory and Input/Output

    • These are communication systems that transfer data between the components inside a computer, or between computers

    • There are 3 types of buses:

      • The data bus carries data

      • The address bus carries the addresses where data must be picked up or stored

      • The control bus carries signals relating to the control and coordination of all the activities within the computer

  • Memory (RAM)

    • The memory unit stores both data and instructions for processing

    • These are stored in the same format

    • The memory is divided into cells, each of which can be accessed by their address

    • The memory is a linear or sequential array of bytes

Harvard Architecture A Level Computer Science

• In A Level Computer Science, Harvard architecture includes:

  • Separate Instruction and Data Memory

    • In Harvard architecture, the system has separate memory units for storing data and instructions

    • This separation provides greater speed and efficiency as the system can fetch data and instructions simultaneously from separate buses, without one interfering with the other

  • Separate Instruction and Data Buses

    • Harvard architecture uses separate buses for data and fetching instructions, meaning that data transfers do not interfere with instruction fetches

    • This can lead to better overall system performance

  • Control Unit (CU)

    • The control unit controls the operation of the processor and its components

    • It retrieves instructions stored in memory, decodes or interprets them, and then executes them

    • The CU generates timing signals and controls the other units of the computer

  • Arithmetic Logic Unit (ALU)

    • The ALU carries out all the arithmetic and logic operations in the computer such as:

      • Addition

      • Subtraction

      • Multiplication

      • Division

      • Comparisons, etc.

How does Harvard architecture improve performance over Von Neumann architecture?

• There are several things that Harvard architecture has or can do which can improve performance over Von Neumann architecture: