View source for Graphics address remapping table

{{short description|I/O memory management unit for graphics}}
The '''graphics address remapping table''' ('''GART'''),<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> also known as the '''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> or '''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 I/O memory management unit (IOMMU) used by [[Engineering:Accelerated Graphics Port|Accelerated Graphics Port]] (AGP) and [[Engineering:PCI Express|PCI Express]] (PCIe) [[Engineering:Graphics card|graphics card]]s. The GART allows the graphics card [[Direct memory access|direct memory access]] (DMA) to the host system memory, through which buffers of [[Texture mapping|textures]], [[Polygon mesh|polygon mesh]]es and other data are loaded. [[Engineering:AMD|AMD]] later reused the same mechanism for I/O virtualization with other peripherals including [[Engineering:Disk controller|disk controller]]s and network adapters.<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>

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 [[Texture mapping|textures]], [[Polygon mesh|polygon mesh]]es 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 [[Engineering:Intel HD Graphics|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. 

==Operating system support==

=== Linux ===
Jeff Hartmann served as the primary maintainer of the [[Software:Linux kernel|Linux kernel]]'s agpgart driver, which began as part of Brian Paul's [[Software:Utah GLX|Utah GLX]] accelerated Mesa 3D driver project. The developers primarily targeted Linux 2.4.x kernels, but made patches available against older 2.2.x kernels. Dave Jones heavily reworked agpgart for the Linux 2.6.x kernels, along with more contributions from Jeff Hartmann.<ref>{{cite web |url=http://www.linuxsymposium.org/archives/OLS/Reprints-2003/Reprint-Jones-OLS2003.pdf|title=Ugly Ducklings: Resurrecting unmaintained code – agpgart adapted for Linux 2.6 kernel |format=PDF |date=2003-07-24 |accessdate=2014-06-05 |archiveurl=https://web.archive.org/web/20140203111912/http://www.linuxsymposium.org/archives/OLS/Reprints-2003/Reprint-Jones-OLS2003.pdf |archivedate=2014-02-03 |last=Jones |first=Dave}}</ref>

=== FreeBSD ===
In [[Software:FreeBSD|FreeBSD]], the agpgart driver appeared in its 4.1 release.<ref>{{cite web|url=http://www.freebsd.org/cgi/man.cgi?agpgart |title=agp(4) |work=FreeBSD Man Pages: FreeBSD Kernel Interfaces Manual |publisher=freebsd.org |date=2007-11-28 |accessdate=2014-06-10}}</ref>

=== Solaris ===
AGPgart support was introduced into Solaris Express Developer Edition as of its 7/05 release.<ref>{{cite web
 |url = http://docs.sun.com/app/docs/doc/819-2254/agpgart-io-7i
 |title = agpgart_io manpage
 |accessdate = 2007-12-04
 |work = docs.sun.com
 |publisher = [[Company:Sun Microsystems|Sun Microsystems]]
 |archive-url = https://web.archive.org/web/20090323100129/http://docs.sun.com/app/docs/doc/819-2254/agpgart-io-7i
 |archive-date = 2009-03-23
 |url-status = dead
 }}</ref>

== See also ==
* [[Software:Direct Rendering Manager|Direct Rendering Manager]]

== References ==
{{Reflist}}

[[Category:Graphics hardware]]

{{Sourceattribution|Graphics address remapping table}}