|
Multiprocessing is the use of two or more central processing units (CPUs) within a single computer system.〔 The term also refers to the ability of a system to support more than one processor and/or the ability to allocate tasks between them.〔(Chip multiprocessing )〕 There are many variations on this basic theme, and the definition of multiprocessing can vary with context, mostly as a function of how CPUs are defined (multiple cores on one die, multiple dies in one package, multiple packages in one system unit, etc.). According to some on-line dictionaries, a multiprocessor is a computer system having two or more processing units (multiple processors) each sharing main memory and peripherals, in order to simultaneously process programs.〔http://www.yourdictionary.com/multiprocessor〕〔http://www.thefreedictionary.com/multiprocessor〕 A 2009 textbook defined multiprocessor system similarly, but noting that the processors may share "some or all of the system’s memory and I/O facilities"; it also gave tightly coupled system as a synonymous term. At the operating system level, ''multiprocessing'' is sometimes used to refer to the execution of multiple concurrent processes in a system, with each process running on a separate CPU or core, as opposed to a single process at any one instant. When used with this definition, multiprocessing is sometimes contrasted with multitasking, which may use just a single processor but switch it in time slices between tasks (i.e. a time-sharing system). Multiprocessing however means true parallel execution of multiple processes using more than one processor.〔 Multiprocessing doesn't necessarily mean that a single process or task uses more than one processor simultaneously; the term parallel processing is generally used to denote that scenario.〔 Other authors prefer to refer to the operating system techniques as multiprogramming and reserve the term ''multiprocessing'' for the hardware aspect of having more than one processor. The remainder of this article discusses multiprocessing only in this hardware sense. In Flynn's taxonomy, multiprocessors as defined above are MIMD machines.〔 As they are normally construed to be tightly coupled (share memory), multiprocessors are not the entire class of MIMD machines, which also contains message passing multicomputer systems. == Pre-history == According to a 1985 article in ''Byte'', possibly the first expression of the idea of multiprocessing is found in the 1842 words of Luigi Federico Menabrea, which said about Charles Babbage's analytical engine (as translated by Ada Lovelace): "the machine can be brought into play so as to give several results at the same time, which will greatly abridge the whole amount of the processes."〔(Multiprocessing ), BYTE magazine Volume 10, Number 05 (May 1985), p. 169.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Multiprocessing」の詳細全文を読む スポンサード リンク
|