Graphics address remapping table: Difference between revisions

Revision as of 23:47, 24 March 2018

Revision as of 23:58, 24 March 2018

Line 1:

The '''graphics address remapping table'''<ref>{{Cite book|url=http://esd.cs.ucr.edu/webres/agp20.pdf|title=Accelerated Graphics Port Interface Specification: Revision 2.0|date=4 May 1998|pages=24}}</ref> or '''graphics aperture remapping table'''<ref>{{Cite book|url=http://www.playtool.com/pages/agpcompat/agp30.pdf|title=AGP V3.0 Interface Specification|date=September 2002|pages=116}}</ref> ('''GART'''), sometimes also '''graphics translation table''' ('''GTT'''),<ref>{{cite web|author=freedesktop.org|url=http://dri.freedesktop.org/wiki/GART|title=GART|accessdate=2010-03-05}}</ref> is an [[IOMMU|I/O memory management unit]] (IOMMU) used by [[Accelerated Graphics Port]] (AGP) and [[PCI Express]] (PCIe) [[graphics card]]s. The GART allows the graphics card [[direct memory access]] (DMA) to the host system memory, through which buffers of [[texture mapping|textures]], [[polygon mesh]]es and other data are loaded. [[AMD]] later reused the same mechanism for [[I/O virtualization]] with other peripherals including [[disk controller]]s and [[network adapter]]s.<ref>[https://support.amd.com/TechDocs/48882_IOMMU.pdf AMD I/O Virtualization Technology (IOMMU) Specification, 32-bit to 64-bit Legacy I/O Device Mapping]</ref>

GART is used as a means of data transferexchange between the [[primary storage|main memory]] and [[video memory]] through which buffers (i.e. paging/swapping) of [[texture mapping|textures]], [[polygon mesh]]es and other data are loaded, but can also be used to expand the amount of video memory available for graphics cards, particularly for cards with no dedicated video memory such as [[Intel HD Graphics]] processors. However, this type of memory (expansion) remapping has repercussions that affect the entire system: specifically, any GART, pre-allocated memory becomes pooled and cannot be used for any other purpose but graphics memory usage (i.e solely as a virtual vRAM buffer).

==Operating System Support==