Von Neumann and Harvard Machine Architecture

Von Neumann and Harvard Machine Architecture – A computer can be defined as a device that can store, process, and retrieve data as and when required. Most of the computer systems can be divided into three subsystems

1. Processor
2. Memory
3. Input/Output devices

Based on these three subsystems, the computer architecture can be classified as follows:

1. Von Neumann Machine Architecture
2. Harvard Machine Architecture

Von Neumann and Harvard Machine Architecture

Von Neumann Machine Architecture

A Von Neumachine has three hardware subsystems: a CPU, a main memory, and an I/O system. It is a stored program computer. The stored program concept is that first, the program and data needed by that program are stored in the main memory, and then the processor fetches instructions and executes them one by one, The instructions need not be entered each time, when they are processed. One of the developers of this concept was John Von Neumann, therefore, such computers are named after Von Neumann Computers.

Is Von Neumans machine architecture, data and code (instructions) are stored in the main memory without differentiating these words (bytes) from one another It means that the data and program storage are in the same memory address space, below figure shows the memory architecture of a computer that is based on Von Neumann architecture with n-bits representing A memory address.

Harvard Machine Architecture

Harvard machine architecture also has three hardware subsystems: a CPU, a memory and an I/O system. In this architecture the program code and data are stored at separate memory blocks.

Each memory block has a starting address from 0. Below figure shows the memory structure in the Harvard machine architecture.