| Single Instruction |
Multiple Instruction |
|
|---|---|---|
| Single Data |
SISD | MISD |
| Multiple Data |
SIMD | MIMD |
Flynn's taxonomy is a classification of computer architectures, proposed by Michael J. Flynn in 1966. In Computing, SISD ( S ingle I nstruction S ingle D ata is a term referring to an architecture in which a single processor an uniprocessor In Computing, MISD ( M ultiple I nstruction S ingle D ata is a type of Parallel computing architecture where In Computing, SIMD ( S ingle I nstruction M ultiple D ata is a technique employed to achieve data level parallelism as in a Vector In Computing, MIMD ( M ultiple I nstruction stream M ultiple D ata stream is a technique employed to achieve parallelism In Computer engineering, computer architecture is the conceptual design and fundamental operational structure of a Computer system Michael J Flynn (born May 20, 1934 in New York City) is an American professor emeritus at Stanford University [1][2]
Contents |
Classifications
The four classifications defined by Flynn are based upon the number of concurrent instruction (or control) and data streams available in the architecture:
- Single Instruction, Single Data stream (SISD)
- A sequential computer which exploits no parallelism in either the instruction or data streams. In Computing, SISD ( S ingle I nstruction S ingle D ata is a term referring to an architecture in which a single processor an uniprocessor Examples of SISD architecture are the traditional uniprocessor machines like a PC or old mainframes. A uniprocessor system is a Computer system with a single Central processing unit. A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated Mainframes (often colloquially referred to as Big Iron) are Computers used mainly by large organizations for critical applications typically bulk data
- Single Instruction, Multiple Data streams (SIMD)
- A computer which exploits multiple data streams against a single instruction stream to perform operations which may be naturally parallelized. In Computing, SIMD ( S ingle I nstruction M ultiple D ata is a technique employed to achieve data level parallelism as in a Vector For example, an array processor or GPU. A vector processor, or array processor, is a CPU design where the instruction set includes operations that can perform mathematical operations on multiple data
- Multiple Instruction, Single Data stream (MISD)
- Multiple instructions operate on a single data stream. In Computing, MISD ( M ultiple I nstruction S ingle D ata is a type of Parallel computing architecture where Uncommon architecture which is generally used for fault tolerance. Heterogeneous systems operate on the same data stream and must agree on the result. Examples include the Space Shuttle flight control computer. NASA 's Space Shuttle, officially called the Space Transportation System ( STS) is the Spacecraft currently used by the United States
- Multiple Instruction, Multiple Data streams (MIMD)
- Multiple autonomous processors simultaneously executing different instructions on different data. In Computing, MIMD ( M ultiple I nstruction stream M ultiple D ata stream is a technique employed to achieve parallelism Distributed systems are generally recognized to be MIMD architectures; either exploiting a single shared memory space or a distributed memory space. Distributed computing deals with Hardware and Software Systems containing more than one processing element or Storage element concurrent
Diagram comparing Classifications
Visually, these four architectures are shown below where each "PU" is a processing unit:
-
SISD MISD 
SIMD MIMD 
Further Divisions
As of 2006, all the top 10 and most of the TOP500 supercomputers are based on a MIMD architecture. The TOP500 project ranks and details the 500 most powerful known Computer systems in the world A supercomputer is a Computer that is at the frontline of processing capacity particularly speed of calculation (at the time of its introduction
Some further divide the MIMD category into the following categories:[1][2][3][4][5]
- Single Program, Multiple Data streams (SPMD)
- Multiple autonomous processors simultaneously executing the same program (but at independent points, rather than in the lockstep that SIMD imposes) on different data. In Computing, SPMD ( S ingle P rocess M Lockstep systems are redundant computing systems that run the same set of operations at the same time in parallel. Also referred to as 'Single Process, multiple data'[6]. SPMD is the most common style of parallel programming[7].
- Multiple Program Multiple Data (MPMD)
- Multiple autonomous processors simultaneously operating at least 2 independent programs. Typically such systems pick one node to be the "host" ("the explicit host/node programming model") or "manager" (the "Manager/Worker" strategy), which runs one program that farms out data to all the other nodes which all run a second program. Those other nodes then return their results directly to the manager.
Even further subdivisions are sometimes considered[8].
References
- ^ Flynn, M. , Some Computer Organizations and Their Effectiveness, IEEE Trans. Comput. , Vol. C-21, pp. 948, 1972.
- ^ Duncan, Ralph, "A Survey of Parallel Computer Architectures", IEEE Computer. February 1990, pp. 5-16.
This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL. The Free On-line Dictionary of Computing ( FOLDOC) is an online searchable encyclopedic Dictionary of Computing subjects The GNU Free Documentation License ( GNU FDL or simply GFDL) is a Copyleft License for free documentation designed by the Free Software
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