graphics address remapping table

{{short description|I/O memory management unit for graphics}}

The graphics address remapping table (GART),{{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}} also known as the graphics aperture remapping table,{{Cite book|url=http://www.playtool.com/pages/agpcompat/agp30.pdf|title=AGP V3.0 Interface Specification|date=September 2002|pages=116}} or graphics translation table (GTT),{{cite web|author=freedesktop.org|url=http://dri.freedesktop.org/wiki/GART|title=GART|accessdate=2010-03-05}} is an I/O memory management unit (IOMMU) used by Accelerated Graphics Port (AGP) and PCI Express (PCIe) graphics cards. The GART allows the graphics card direct memory access (DMA) to the host system memory, through which buffers of textures, polygon meshes and other data are loaded. AMD later reused the same mechanism for I/O virtualization with other peripherals including disk controllers and network adapters.[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]

A GART is used as a means of data exchange between the main memory and video memory through which buffers (i.e. paging/swapping) of textures, polygon meshes and other data are loaded, but can also be used to expand the amount of video memory available for systems with only integrated or shared graphics (i.e. no discrete or inbuilt graphics processor), such as Intel HD Graphics processors. However, this type of memory (expansion) remapping has a caveat that affects the entire system: specifically, any GART, pre-allocated memory becomes pooled and cannot be utilised for any other purposes but graphics memory and display rendering.