Von Neumann Architecture (OCR GCSE Computer Science)

What is the Von Neumann architecture?

• The Von Neumann Architecture is a design of the CPU which was proposed by Mathematician John Von Neumann in the 1940s, which most general-purpose computers are built upon
• The Von Neumann Architecture outlines how the computer memory, input / output devices and processor all work together 

The Von-Neumann-architecture

• It consists of 4 main registers
  • The Program Counter (PC)
  • The Memory Address Register (MAR)
  • The Memory Data Register (MDR)
  • The Accumulator (ACC)
• For each of the registers you must know 
  • The name of the register
  • Its acronym
  • The purpose of the register

What do each of the registers do?

Program Counter (PC)

• Holds the memory address of the next instructions to be executed 
• Increments by 1 as the fetch-decode-execute cycle runs

Memory Address Register (MAR)

• Holds the memory address of where data or instructions are to be fetched from

Memory Data Register (MDR)

• Stores the data or instruction which has been fetched from memory

Accumulator (ACC)

• Stores the results of any calculations that have taken place in the Arithmetic Logic Unit (ALU)