Flynn's classification, proposed by Michael J. Flynn in 1966, categorizes computer architectures based on instruction and data streams into four types: SISD, SIMD, MIMD, and MISD. Each type represents different organization structures and processing capabilities, with SISD being the most conventional and MIMD commonly used in multiprocessor systems. The conclusion highlights the limitations of this classification in addressing the complexity of modern parallel computing architectures.

1. Flynn’s Classification
Presented By: Bishal Adhikari
Roll No.: 7

2. In 1966, Michael J. Flynn proposed a classification for computer architectures
based on the number of instruction streams and data streams(Flynn’s Taxonomy).
● Flynn’s Classification refers to a classification of parallel computer
architectures and machine’s structure.
● The sequence of instructions read from memory is called an instruction
stream. The operations performed on the data in the processor is called
a data stream.
Flynn’s Classification
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3. Types of Flynn’s Classification
SISD(Single Instruction Single Data)
SIMD(Single Instruction Multiple Data)
MIMD(Multiple Instruction Multiple Data)
MISD(Multiple Instruction Single Data)
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SISD(Single Instruction Single Data)

6. SISD(Single Instruction Single Data)
● Most conventional machines with one CPU containing a single
arithmetic – logic unit.
● SISD represents the organization of a single computer containing a
control unit, a processor unit, and a memory unit.
● Instructions are executed sequentially and the system may or may not
have internal parallel processing capabilities.
● In SISD computer instructions are executed sequentially but may
overlap in their execution stages.
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SIMD(Single Instruction Multiple Data)

8. SIMD(Single Instruction Multiple Data)
● This category corresponds to array processors. They have multiple
processing/execution units and one control unit.
● SIMD represents an organization that includes many processing units
under the supervision of a common control unit.
● All processors receive the same instruction from the control unit but
operate on different items of data.
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MIMD(Multiple Instruction Multiple Data)

10. MIMD(Multiple Instruction Multiple Data)
● There is no computer at present that can be classified as MISD. Mostly
used in pipelined computers.
● Each receiving distinct instructions operating over the same data
stream and its derivatives.
● The result of one processor become the input of the next processor in
the micro-pipe.
● MISD structure is only of theoretical interest since no practical system
has been constructed using this organization.
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MISD(Multiple Instruction Single Data)

12. MISD(Multiple Instruction Single Data)
● Most multiprocessor system and multiple computer system can be
classified in this category.
● In MIMD, there are more than one processor unit having the ability to
execute several programs simultaneously.
● MIMD organization refers to a computer system capable of processing
several programs at the same time.
● Contains multiple processing units. Execution of multiple instructions
on multiple data.
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13. Conclusion
In conclusion, while Flynn's Classification is well-established
and familiar in parallel programming, its limitation in
providing only four slots and the changing landscape of
parallel computing technologies pose challenges. The
system's granularity may be too coarse, resembling a binary
division of computers into parallel and sequential, which
oversimplifies the complex range of parallel computing
architectures.
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