View source for Aperture (computer memory)

{{Notability|date=March 2025}}
In [[computing]], an '''aperture''' is a portion of [[physical address]] space (i.e. [[Computer_data_storage#Primary_storage|physical memory]]) that is associated with a particular [[peripheral device]] or a [[computer memory|memory]] unit. Apertures may reach external devices such as [[read-only memory|ROM]] or [[random access memory|RAM]] chips, or internal memory on the [[central processing unit|CPU]] itself.

Typically, a memory device attached to a computer accepts addresses starting at zero, and so a system with more than one such device would have ambiguous addressing. To resolve this, the memory logic will contain several aperture [[multiplexer|selectors]], each containing a range selector and an interface to one of the memory devices. 

The set of selector address ranges of the apertures are disjoint. When the CPU presents a physical address within the range recognized by an aperture, the aperture unit routes the request (with the address remapped to a zero base) to the attached device. Thus, apertures form a layer of [[address space|address translation]] below the level of the usual virtual-to-physical mapping.

==See also==
* [[Address bus]]
* [[AGP aperture]]
* [[Memory-mapped I/O]]

==References==
* {{cite book |title=AGP System Architecture |pages=49–62 |first1=Dave|last1=Dzatko |first2=Tom |last2=Shanley |url=https://books.google.com/books?id=u6RE2pcMeYoC&dq=Aperture+memory+addresses&pg=PA52|year=2000|publisher=Addison Wesley Longman |author3=MindShare, Inc|isbn=978-0-201-70069-5 }}
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[[Category:Computer memory]]
[[Category:Computer architecture]]

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