Feng’s classification
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Feng's Classification from 1972 classified computer architectures based on their degree of parallelism. It defined the maximum degree of parallelism P as the maximum number of bits that can be processed within a unit of time. Architectures were classified into four categories based on whether processing occurred at the word and bit level serially or in parallel: word serial/bit serial, word parallel/bit serial, word serial/bit parallel, and word parallel/bit parallel. The degree of parallelism P is calculated as the product of the number of bits in a word and the number of words processed in parallel.
Feng’s classification
- 1. Feng’s Classification Narayan Kandel 071/MSCSKE/657
- 2. Classification of computer Architectures Flynn’s Classification (1966): is based on the multiplicity of instruction stream and data stream in a computer system. Feng’s Classification (1972): is based on serial versus parallel processing. Handler’s Classification (1977): is determined by the degree of parallelism and pipelining in various subsystem levels. 2
- 3. Feng’s Classification ● Feng (1972) has proposed the use of degree of parallelism to classify various computer architectures. ● The maximum number of binary digits(bits) that can be processed within a unit time by a computer system is called maximum degree of parallelism P. ● Let us Pi be the number of bits that can be processed within the ith processor cycle. Consider processor cycles indexed by i=1,2,3…,T. The average degree of parallelism, Pa is given by ● In general, Pi≤P. We define the utilization rate μ of a computer system within T cycles is ● If the computing power is fully utilized (or the parallelism is fully exploited), we have Pi=P for all I and μ=1 for 100 percent utilization. The utilization rate depends on the application program being executed. 3
- 4. Classification based on Word/Bit Count Classification based on sequential and parallel operation at bit and word levels : 1) Word Serial and Bit Serial (WSBS): also called as Bit Serial Processing (1 bit is processed at time); slow 2) Word Parallel and Bit Serial (WPBS): also called as Slice processing (m bit slice at a time) 3) Word Serial and Bit Parallel (WSBP): also called as word slice processing (1 word of n bit at time) 4) Word Parallel and Bit Parallel (WPBP): also known as fully parallel processing; fastest The maximum degree of parallelism P is given by the product of the number of bits in a word(n) and number of words in parallel(m). P= m.n 4
- 5. Example word length (n) 5 1) Word Serial and Bit Serial (WSBS) (1, 1) 2) Word Parallel and Bit Serial (WPBS) (*, 1) 3) Word Serial and Bit Parallel (WSBP) (1, *) 4) Word Parallel and Bit Parallel (WPBP) (*, *) * ---> greater than 1
- 6. Example... Degree of Parallelism -> area of rectangle 6
- 7. Limitation 1. Fails to project the concurrency in pipeline processors as degree of parallelism doesn’t account for concurrency handle by pipelined design Handler’s schema allow pipeline to be specific... 7
- 8. References... 1. Advanced Computer Architecture & Computing By S.S.Jadhav, Revised Edition 2009, Technical Publication Pune. 2. Parallel Computing By Moreshwar R. Bhujade , New AGE international Publishers. 8
- 9. THANK YOU! 9 Narayan Kandel Email: npkand@gmail.com