Why Use Parallel Computing? The primary reasons for using parallel computing Other reasons might include Limits to serial computing - both physical and practical   reasons pose significant constraints to simply building ever faster serial computers. There are different ways to classify parallel computers. One of the more widely used classifications, in use since 1966, is called Flynn's Taxonomy. The 4 possible classifications according to Flynn: S I S D Single Instruction, Single Data S I M D Single Instruction, Multiple Data M I S D Multiple Instruction, Single Data M I M D Multiple Instruction, Multiple Data