Fengs’s Classification

Parallel computing refers to the process of executing several processors or applications simultaneously. It is a kind of architecture where large problems break into smaller or usually similar parts that can be processed in one go. Parallel computing helps in faster application processing and task resolution.

There are various architectural schemes defined in order to achieve parallel computing. I.e. Flynn’s taxonomy, Feng’s Classification, Handler’s Classification, etc.

Feng’s Classification

Tse-yun Feng proposed a system for classifying the parallel processing system. This classification is based on the number of bits in a word and word length. This parallelism is based on the parallelism of bits and words. Hence we can have the bits of word processed in parallel or serially. Similarly, we can have words processed in parallel or serially. Thus resulting in the following four categories-

1. Word Serial Bit Serial (WSBS) 

In this case, one bit of a selected word is processed at a time. This corresponds to serial processing and hence requires maximum processing time.

2. Word Serial Bit Parallel (WSBP)

In this case, all the bits of a selected word are processed simultaneously, but one word at a time. Hence bit parallel indicates the selection of all the bits of a word. Hence it is slightly parallel processing. 

3. Word Parallel Bit Serial (WPBS)

In this case, one selected bit from all the specified words is processed at a time. Hence word parallel indicates the selection of multiple words. WSBP can be said to be row parallelism while WPBS can be said as column parallelism.

4. Word Parallel Bit Parallel (WPBP)

In this case, all the bits of all the specified words are operated on simultaneously. Hence this gives the maximum parallelism thereby minimum time for execution. The processors are classified according to Feng’s Classification can be shown in the graphical representation with a number of bits vs numbers of words in parallel. The below figure shows this graphical representation.

• Processors like IBM370, Cray-1, and PDP11 have words executed in parallel but the word size varies from 16 to 64 bits. Thus these processes can be said to be  WSBP ( Word Serial Bit Parallel ) processors. 
• STARAN and MPP processors have one bit of a word executed at a time but multiple words together. These processors can hence be categorized under  WPBS ( Word Parallel Bit Serial ).
• Processors like  C.mmp and PEPE are having multiple bits and multiple words being executed simultaneously and hence can be categorized under WPBP ( Word Parallel Bit Parallel ).