Question

Briefly describe the von Neumann Machine.

Answer 1

VON NEUMANN MACHINE:

The Von Neumann architecture is about the structure that a computer should follow. Most of the computers today follow this framework. Among the principles enunciated in the paper were that data and instructions should be kept in a single store and that instructions should be encoded so as to be modifiable by other instructions. It is also known as IAS Computer. A Von Neumann-based computer has the following characteristics:

1)Utilises a single processor

2)Utilises one memory for both instructions and data

3)Implements programs by executing one instruction at a time

Components of Von Neumann Architecture

The Von Neumann Architecture has the following components:

1)Central Processing Unit (CPU)

2)Immediate Access Store (IAS)

3)Input / Output (I/O)

Central Processing Unit

The CPU governs the computer and handles the data. It has four main parts as follows:

1)Arithmetic Logic Unit(ALU)

This part handles all the arithmetic and logic operations such as calculations and comparisons.

2)Control Unit

This part handles the movement of instructions to and from the memory and the execution of instructions one at a time.

3)Registers

There are different types of registers depending on the information being stored.

• Program Counter(PC) – stores location of next instruction

• Current Instruction Register(CIR) – stores current instruction being implemented

• Accumulators – store results of calculations and comparisons

• Status Register – stores data about the last operation

• Interrupt Register(IR) – stores information regarding an interruption that occurred

4)Clock

Instructions are executed to the beat of the clock. The faster the clock, the faster the computer is.

Immediate Access Store

This is commonly referred to as the Random Access Memory (RAM) or Main Memory. It stores both instructions and data. Before Von Neumann, computers used to divide memory into instructions memory and data memory, which made it complex. Von Neumann discovered that there’s no difference between the nature of an instruction and the nature of data.
Buses which allow the movement of instructions and data between different parts of the computer is called a data bus. Buses that detect locations in memory is called an address bus.

Input / Output

I/O refers to the accessories for inputting and outputting of data. A computer needs to read in data and send out data through I/O ports. An I/O controller is an interface that allows a user to attach any I/O device to the computer and send data in or out of the computer.

-BASIC CPU STRUCTURE

Advantages of Von Neumann Architecture

Here are some advantages of the Von Neumann architecture:

1)Control Unit retrieves data and instruction in the same manner from one memory. Design and development of the Control Unit is simplified, faster. Cost is less as well.

2)Data from input or output devices and from memory are retrieved in the same manner.

3)Organisation of memory is done by programmers which allows them to utilise the memory’s whole capacity.

Disadvantages of Von Neumann Architecture

Here are some disadvantages of the Von Neumann architecture:

1)Parallel implementation of program is not allowed due to sequential instruction processing.

2)Von Neumann bottleneck – Instructions can only be carried out sequentially and one at a time.

3)There is a risk of an instruction being rewritten due to an error in the program.