Handbook of Computer Science(cs) and IT

Parallel Processing

Parallel processing provides simultaneous data processing tasks for the purpose of increasing the computational speed of a computer system rather than each instruction is processed sequentially, a parallel processing system is able to perform concurrent data processing to achieve faster execution time and increase throughput.

There are more advantages with parallel processing but it has some issues also. Due to parallel processing, the amount of hardware increases and the cost of system increases. Parallel processing is established by distributing the data among the multiple functional units.

Flynn’s Classification

• MJ Flynn introduced the parallel processing classification.
• This classification considers the organisation of a computer system by the number of instructions and data items that are manipulated

Key Points

• The sequence of instructions read from the memory constitutes an instruction
• The operations performed on the data in the processor constitutes a data

r- Flynn’s Classification

Flynn’s classification divides computer into four major groups as follows ‘

• Single Instruction stream, Single Data stream (SISD)
• Single Instruction stream, Multiple Data stream (SIMD)
• Multiple Instruction stream, Single Data stream (MISD)
• Multiple Instruction stream, Multiple Data stream (MIMI)

SISD

It represents the organisation of a single computer containing a control unit, a processor unit and a memory unit. Instructions are executed sequentially.

 

 

SIMD

It represents an organisation that includes many processing units under the supervision of a common control unit. All processors receive the sam_e instruction from the control unit but operate on different items of data.

 

 

 

MISD

Its architecture contains n processors unit, each receiving instruction streams and providing the same data stream. MISD structure is only of theoretical interest, since no practical system has been constructed using this organisation.

 

 

MIMD

Its organisation refers to a computer system capable of processing several programs at the same time.