Von Neumann

Main components

• Central Processing Unit (CPU): Executes instructions. It includes:
  • Control Unit: Coordinates instruction execution.
  • Arithmetic and Logic Unit (ALU): Performs mathematical and logical operations.
• Memory: Stores instructions and data in the same memory space.
• Input/Output Units (I/O): Allow communication with the user or other systems (keyboard, screen, etc.).
• Communication Bus: Links different components for data, instruction and command transfer.

Main characteristics

1. Shared storage: Instructions (program) and data share the same memory.
2. Sequential execution: Instructions are executed one by one, except in special cases (modern multithreading or pipelines).
3. Execution cycle: The CPU operates according to a three-step cycle:
   • Fetch: Reading the instruction from memory.
   • Decode: Decoding the instruction.
   • Execute: Executing the instruction.

Advantages

• Design simplicity: Instructions and data are managed in the same memory space.
• Flexibility: Allows execution of various programs.
• Basis for programmable computers.

Limitations

• Von Neumann bottleneck: Transfer between memory and processor can be slow compared to processing speed.
• Corruption risk: An erroneous instruction can overwrite important data or instructions, as they share the same memory.

Conclusion

Von Neumann architecture remains fundamental for understanding computer operation. Although modern models (like Harvard architecture) have been developed to address some of its limitations, it remains a central concept taught in computer science.