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The term memory hierarchy is used in computer architecture when discussing performance issues in computer architectural design, algorithm predictions, and the lower level programming constructs such as involving locality of reference. A "memory hierarchy" in computer storage distinguishes each level in the "hierarchy" by response time. Since response time, complexity, and capacity are related,〔 the levels may also be distinguished by the controlling technology. The many trade-offs in designing for high performance will include the structure of the memory hierarchy, i.e. the size and technology of each component. So the various components can be viewed as forming a hierarchy of memories (m1,m2,...,mn) in which each member mi is in a sense subordinate to the next highest member mi+1 of the hierarchy. To limit waiting by higher levels, a lower level will respond by filling a buffer and then signaling to activate the transfer. There are four major storage levels. # ''Internal'' – Processor registers and cache. # Main – the system RAM and controller cards. # On-line mass storage – Secondary storage. # Off-line bulk storage – Tertiary and Off-line storage. This is a general memory hierarchy structuring. Many other structures are useful. For example, a paging algorithm may be considered as a level for virtual memory when designing a computer architecture, and one can include a level of nearline storage between online and offline storage. ==Example use of the term== Here are some quotes. * Adding complexity slows down the ''memory hierarchy''.〔Write-combining〕 * CMOx memory technology stretches the Flash space in the memory hierarchy〔(【引用サイトリンク】url=http://www.unitysemi.com/applications-memory-hierarchy.html )〕 * One of the main ways to increase system performance is minimising how far down the memory hierarchy one has to go to manipulate data.〔(【引用サイトリンク】url=http://www.pixelbeat.org/docs/memory_hierarchy/ )〕 * Latency and bandwidth are two metrics associated with caches and memory. Neither of them is uniform, but is specific to a particular component of the memory hierarchy. * Predicting where in the memory hierarchy the data resides is difficult.〔 * ...the location in the memory hierarchy dictates the time required for the prefetch to occur.〔 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「memory hierarchy」の詳細全文を読む スポンサード リンク
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