Graphics address remapping table: Difference between revisions

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

The '''graphics address remapping table''' ('''GART)'''),<ref>{{Cite sometimesbook|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 [[IOMMU|I/O memory management unit]] (IOMMU) used by [[Accelerated Graphics Port|AGP]] (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. It's[[AMD]] usedlater asreused athe meanssame ofmechanism datafor transfer[[I/O betweenvirtualization]] with other peripherals including [[primarydisk storage|physical memorycontroller]]s and [[videonetwork memoryadapter]],s.<ref>[https://support.amd.com/TechDocs/48882_IOMMU.pdf butAMD canI/O alsoVirtualization beTechnology used(IOMMU) toSpecification, expand32-bit theto amount64-bit ofLegacy videoI/O memoryDevice available for graphics cards—particularly for cards with no dedicated video memory, such as Intel integrated graphics.Mapping]</ref>

A GART is used as a means of data exchange 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 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.

==Operating system support==

Jeff Hartmann served as the primary maintainer of the Linux agpgart driver, which began as part of [[Brian Paul]]'s Utah-glx accelerated [[Mesa (computer graphics)|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 2.6x kernels, along with more contributions from Jeff Hartmann.<ref>[http://www.linuxsymposium.org/archives/OLS/Reprints-2003/Reprint-Jones-OLS2003.pdf Ugly Ducklings: Resurrecting unmaintained code] - agpgart adapted for Linux 2.6 kernel</ref>

=== Linux ===

In FreeBSD, the agpgart driver<ref>[http://www.freebsd.org/cgi/man.cgi?agpgart agpgart(4)] - manpage.</ref> appeared in FreeBSD 4.1.

Jeff Hartmann served as the primary maintainer of the [[Linux kernel]]'s agpgart driver, which began as part of [[Brian Paul]]'s [[Utah-glx GLX]] accelerated [[Mesa (computer graphics)|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 2.6x6.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 ===

AGPgart support was introduced into [[Solaris (operating system)#Development release|Solaris Express Developer Edition]] as of its 7/05 release.<ref>{{cite web

In [[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 (operating system)#Development releaseSXDE|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 = [[Sun Microsystems]]

|archive-url = https://web.archive.org/web/20090323100129/http://docs.sun.com/app/docs/doc/819-2254/agpgart-io-7i

}}</ref>

|archive-date = 2009-03-23

|url-status = dead

}}</ref>

==References See also ==

* [[Direct Rendering Manager]]

== References ==

{{Reflist}}

[[Category:Graphics hardware]]

[[Category:Peripheral Component Interconnect]]

{{Compu-graphics-stub}}