(Flynn’s Classification): Flynn’s classification is based on multiplicity of instruction streams and data streams observed by the CPU during program execution. Let Is and Ds are minimum number of streams flowing at any point in the execution, then the computer organization can be categorized as follows:
Single Instruction and Single Data stream (SISD):
In this organization, sequential execution of instructions is performed by one CPU containing a single processing element (PE)
Therefore, SISD machines are conventional serial computers that process only one stream of instructions and one stream of data.
Single Instruction and Multiple Data stream (SIMD):
In this organization, multiple processing elements work under the control of a single control unit.
It has one instruction and multiple data stream
All the processing elements of this organization receive the same instruction broadcast from the CU
Main memory can also be divided into modules for generating multiple data streams acting as a distributed memory as shown in Figure
Multiple Instruction and Single Data stream (MISD):
In this organization, multiple processing elements are organized under the control of multiple control units.
Each control unit is handling one instruction stream and processed through its corresponding processing element.
But each processing element is processing only a single data stream at a time.
Therefore, for handling multiple instruction streams and single data stream, multiple control units and multiple processing elements are organized in this classification.
All processing elements are interacting with the common shared memory for the organization of single data stream as shown in Figure.