Difference Between Von Neumann Architecture and Harvard Architecture

By Admin on

Harvard Architecture:

he name Harvard Architecture comes from the Harvard Mark I relay-based computer. The most obvious characteristic of the Harvard Architecture is that it has physically separate signals and storage for code and data memory. It is possible to access program memory and data memory simultaneously. Typically, code (or program) memory is read-only and data memory is read-write. Therefore, it is impossible for program contents to be modified by the program itself.

  • The name is originated from "Harvard Mark I" a relay based old computer.
  • The computer has two separate memories for storing data and program.
  • Processor can complete an instruction in one cycle if appropriate pipelining strategies are implemented.
  • In the first stage of pipeline the instruction to be executed can be taken from program memory.In the second stage of pipeline data is taken from the data memory using the decoded instruction or address. 
  • Most of the modern computing architectures are based on Harvard architecture.But the number of stages in the pipeline varies from system to system.

Von Neumann Architecture:

The von Neumann Architecture is named after the mathematician and early computer scientist John von Neumann. von Neumann machines have shared signals and memory for code and data. Thus, the program can be easily modified by itself since it is stored in read-write memory.

  • It is named after the mathematician and early computer scientist John Von Neumann.
  • The computer has single storage system(memory) for storing data as well as program to be executed.
  • Processor needs two clock cycles to complete an instruction.Pipelining the instructions is not possible with this architecture.
  • In the first clock cycle the processor gets the instruction from memory and decodes it. In the next clock cycle the required data is taken from memory. For each instruction this cycle repeats and hence needs two cycles to complete an instruction.
  • This is a relatively older architecture and was replaced by Harvard architecture.
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