Editing EXA

{{About|the computer architecture|other uses|Exa (disambiguation)}}
{{short description|Graphics acceleration architecture}}
[[File:Linux graphics drivers 2D.svg|thumb|The XAA/EXA/UXA/SNA APIs are for the 2D graphics drivers inside the [[display server|X server]]. Note, that modern software uses [[Direct Rendering Manager|direct rendering]].]]
[[File:The Linux Graphics Stack and glamor.svg|thumb|[[Glamor (software)|Glamor]] obsoletes [[Device Dependent X|DDX]], here with [[XWayland]].]]
In [[computing]], '''EXA''' is a graphics acceleration architecture of the [[X.Org Server]] (see also [[X Window System]]) designed to replace XAA (the [[XFree86 Acceleration Architecture]])<ref>{{usurped|1=[https://web.archive.org/web/20051118095054/http://www.kdedevelopers.org/node/1122 Summer coding]}} (Zack Rusin [[blog]] entry, 3 June 2005)</ref> and to make the [[X Rendering Extension|XRender]] extension more usable, with only minor changes needed to adapt obsolete [[XFree86]] video drivers written to use XAA; it was designed by [[Zack Rusin]] and announced at [[LinuxTag]] 2005<ref>[http://wiki.x.org/wiki/LinuxTagMeeting2005Zack Acceleration Architecture] (initial LinuxTag presentation by Zack Rusin)</ref> and first released with X.Org Server version 6.9/7.0.

==History==
Historically, a distinction has been made between 2D and 3D acceleration. 2D acceleration was provided by the venerable [[XFree86 Acceleration Architecture]], XAA, which made the video card's 2D hardware acceleration available to the X server.

The 3D acceleration set was provided via the [[Direct Rendering Manager]], which worked by mapping 3D rendered pictures on top of the 2D picture. This had some buggy corner cases, but more or less worked, until [[compositing window manager|compositing]] entered into the desktop. This distinction has become the source of a lot of bugs, and performance problems.

EXA was introduced as a stopgap measure, to provide better integration with [[X Rendering Extension|XRender]] than XAA did, improving the X.Org Server 2D performance. In practice, while this proved quite advantageous in some respects, it also exhibited a number of corner cases and regressions.

The solution was to move to hardware acceleration with [[OpenGL]] for both 2D and 3D graphics with 2D graphics becoming just a subset of 3D rendering. Switching entirely over is unfortunately not so simple and not without some major obstacles.

EXA was adapted from KAA, the [[KDrive]] Acceleration Architecture, from the experimental [[Freedesktop.org]] [[KDrive|Xserver]]. Per the initial mailing list announcement,<ref>[http://lists.freedesktop.org/archives/xorg/2005-June/008321.html New acceleration architecture] (announcement on Xorg mailing list, Zack Rusin, 25 June 2005)</ref> the goals are:

# Properly accelerate XRender
# Be as simple as possible.

Many XAA drivers had EXA support added for X11R6.9/7.0 and support continues to be added to more drivers. Making this transition as easy as possible was an important design consideration.<ref name="exa-driver.txt">{{cite web|url=https://gitlab.freedesktop.org/xorg/xserver/blob/master/hw/xfree86/doc/exa-driver.txt|title=Adding EXA support to your X.Org video driver|author=Jesse Barnes|accessdate=2010-05-18|date=2006-03-09}}</ref>

[[UXA]] is a reimplementation of the EXA API developed by Intel, using the [[Graphics Execution Manager]].<ref>[http://keithp.com/blogs/UMA_Acceleration_Architecture/ UMA Acceleration Architecture]</ref>

The [[Free and open-source graphics device driver#ATI/AMD|Radeon free and open-source device driver]] supports 2D acceleration through EXA and [[Glamor (software)|Glamor]].<ref>{{cite web |url=http://xorg.freedesktop.org/wiki/RadeonFeature/ |title=Radeon Feature Matrix |work=[[freedesktop.org]]}}</ref>

[[Glamor (software)|Glamor]] is supposed to obsolete all previous attempts.<ref>{{cite web |url=http://www.freedesktop.org/wiki/Software/Glamor/ |title=What is Glamor? |work=[[freedesktop.org]]}}</ref>

==Acronym==
According to the X.Org web site<ref>{{cite web|title=Glossary|url=http://www.x.org/wiki/Development/Documentation/Glossary/|publisher=X.Org Foundation|accessdate=29 April 2015}}</ref> ''EXA'' is an ''"acceleration architecture with no well-defined acronym."'' Dot.kde.org called it "Eyecandy Acceleration Architecture".<ref>[http://dot.kde.org/2005/06/28/new-acceleration-architecture-xorg New Acceleration Architecture for X.org] (dot.kde.org, 28 June 2005)</ref> The driver modification guide<ref name="exa-driver.txt"/> calls it "EXcellent Architecture or Ex-kaa aXeleration Architecture or whatever."

==See also==
* [[Direct Rendering Infrastructure]] (DRI)
* [[Mesa 3D]]
* [[EGL (API)|EGL]]
* [[Glamor (software)|Glamor]]
* [[SNA (computer graphics)|SNA]]

==References==
<references/>

==External links==
*[http://xorg.freedesktop.org/wiki/ExaStatus ExaStatus] (X.Org)
*[http://cworth.org/tag/exa/ EXA] (Carl Worth's EXA development blog posts)

{{DEFAULTSORT:Exa}}
[[Category:X-based libraries]]