Harvard and Von-neumann Architecture of computer architecture and difference between them

Computer architecture is the internal structure system and system of functioning of of computer system. There are mainly two architecture of computer system.

1. VON NEUMANN COMPUTER ARCHITECTURE 

2. HARVARD ARCHITECTURE

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In these days, digital system is used everywhere. Audio and video all are digitized to their digital signal by digital signal processor. So harvard architecture gives the use of such digital signal processing system.

1. von neumann architecture 

=> It is named after the mathematician and early computer scientist John Von Neumann.

=> It is used in conventional processors found in PCs and Servers, and embedded systems with only control functions.

=> The data and program are stored in the same memory

=> The code is executed serially and takes more clock cycles

=> There is no exclusive Multiplier

=> There is an Absence of Barrel Shifter

=> The programs can be optimized in lesser size

2. harvard architecture 

=> The name is originated from "Harvard Mark I" a relay based old computer.

=>Used in DSPs and other processors found in latest embedded systems and Mobile communication systems, audio, speech, image processing systems

=>The data and program memories are separate

=>The code is executed in parallel

=>It has MAC (Multiply Accumulate)

=>Barrel Shifter help in shifting and rotating operations of the data

=> The program tend to grow big in size

DESCRIPTION 

There are two basic Computer architectures:
-Harvard Architecture
-Princeton Architecture(Von Neumann Architecture)

In Harvard Architecture, the CPU can have separate data and instruction memory and busses, allowing transfers to be performed simultaneously on both busses.

In Von Neumann architecture, the CPU can be either reading an instruction or reading/writing data from/to the memory. Both cannot occur at the same time since the instructions and data use the same bus system.

Harvard architecture machine have distinct code and data address spaces: instruction address zero is not the same as data address zero. Instruction address zero might identify a twenty-four bit value, while data address zero might indicate an eight bit byte that isn’t part of that twenty-four bit value. While in Von Neumann architecture, Instruction and Data addresses are same.

In Harvard architecture, Processor can execute an instruction in one clock cycle, if appropriate pipelining strategies are implemented. In the first stage of pipeline, the instruction to be executed is fetched from program memory and decoded. In the second stage, data is taken from the data memory using the decoded instruction or address.While in von Neumann architecture, Processor needs two clock cycles to complete an instruction. Pipelining the instructions is not possible.

The Von Neumann architecture’s largest advantage is that it simplifies the microcontroller chip design because only one memory is accessed. For microcontrollers, its biggest asset is that the contents of RAM (random-access memory) can be used for both variable (data) storage as well as program instruction storage. An advantage for some applications is the program counter stack contents that are available for access by the program. This allows greater flexibility in developing software, primarily in the areas of real-time operating systems.

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