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 vs Harvard Architecture

  
• Von Neumann

  
• Von Neumann's architecture includes: 

  - Control Unit

  - Arithmetic Logic Unit

  - Special Registers

  - Busses

  - Random Access Memory
• Von Neumann - 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 
• Von Neumann - Arithmetic Logic Unit (ALU) 

  • The ALU carries out all the arithmetic and logic operations in the computer such as: 
  • Addition 
  • Subtraction 
  • Multiplication 
  • Division 
  • Comparisons
• Von Neumann - Buses

  • 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
• Von Neumann - 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

  
• Harvard architecture includes: 

  • Separate Instruction and Data Memory
  • Separate Instruction and Data Buses 
  • Control Unit (CU) 
  • Arithmetic Logic Unit (ALU) 
• Harvard Architecture - 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 
• Harvard Architecture - 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 
• Harvard Architecture - 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 
• Harvard Architecture - Arithmetic Logic Unit (ALU) 

  • The ALU carries out all the arithmetic and logic operations in the computer such as: 
  • Addition 
  • Subtraction 
  • Multiplication 
  • Division 
  • Comparisons
• 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: