Editing Accelerated Graphics Port (section)

==Versions==
{| class="wikitable floatright" style="text-align: left; margin-left: 1.5em;"
|+ AGP and [[Peripheral Component Interconnect|PCI]]: [[32-bit computing|32-bit]] buses operating at 66 and 33&nbsp;[[megahertz|MHz]] respectively
|-
!Specification || Voltage || Clock || Speed || Transfers/<br>clock || Rate (MB/s)
|-
|PCI || 3.3/5&nbsp;V || 33&nbsp;MHz || {{0}}&mdash; || {{0|000}}1 || {{0}}133
|-
|PCI 2.1 || 3.3/5&nbsp;V || 33/66&nbsp;MHz || {{0}}&mdash; || {{0|000}}1 || {{0}}133/266
|-
|AGP 1.0 || 3.3&nbsp;V || 66&nbsp;MHz || {{0}}1× || {{0|000}}1 || {{0}}266
|-
|AGP 1.0 || 3.3&nbsp;V || 66&nbsp;MHz || {{0}}2× || {{0|000}}2 || {{0}}533
|-
|AGP 2.0 || 1.5&nbsp;V || 66&nbsp;MHz || {{0}}4× || {{0|000}}4 || 1066
|-
|AGP 3.0 || 0.8&nbsp;V || 66&nbsp;MHz || {{0}}8× || {{0|000}}8 || 2133
|-
|AGP 3.5<sup>*</sup> || 0.8&nbsp;V || 66&nbsp;MHz || {{0}}8× || {{0|000}}8 || 2133<ref>{{cite book | url=https://books.google.com/books?id=9cLFf_1PBnkC&dq=agp+2133&pg=PT268 | isbn=978-0-13-279698-9 | title=Upgrading and Repairing Servers | date=24 April 2006 | publisher=Pearson Education }}</ref>
|}

Intel released "AGP specification 1.0" in 1997.<ref name=agp10/> It specified 3.3&nbsp;V signals and 1× and 2× speeds.<ref name=Intel440LXdata /> Specification 2.0 documented 1.5&nbsp;V signaling, which could be used at 1×, 2× and the additional 4× speed<ref>{{cite web |url=http://www.smartcomputing.com/editorial/article.asp?article=articles/archive/g0801/35x01/04g01.asp |title=AGP 4×: Faster Data Transfer & Better-Quality Images |access-date=15 September 2014|archive-url=https://web.archive.org/web/20071115042348/http://www.smartcomputing.com/editorial/article.asp?article=articles/archive/g0801/35x01/04g01.asp|archive-date=15 November 2007 |url-status=dead}}</ref><ref name=agp20 /> and 3.0 added 0.8&nbsp;V signaling, which could be operated at 4× and 8× speeds.<ref name=agp30/> (1× and 2× speeds are physically possible, but were not specified.)

Available versions are listed in the adjacent table.

AGP version 3.5 is only publicly mentioned by Microsoft under ''Universal Accelerated Graphics Port (UAGP)'', which specifies mandatory supports of extra registers once marked optional under AGP 3.0. Upgraded registers include PCISTS, CAPPTR, NCAPID, AGPSTAT, AGPCMD, NISTAT, NICMD. New required registers include APBASELO, APBASEHI, AGPCTRL, APSIZE, NEPG, GARTLO, GARTHI.

There are various physical interfaces (connectors); see the [[#Compatibility|Compatibility]] section.

===Official extensions===
[[File:NVIDIA GeForce4 Ti 4600 Mac.jpg|thumb|AGP graphics card (Apple [[Macintosh]])]]
[[File:Quadro ELSA GLoria II Pro.jpg|thumb|AGP Pro graphics card]]

====AGP Pro====
An official extension for cards that required more electrical power, with a longer slot with additional pins for that purpose. AGP Pro cards were usually workstation-class cards used to accelerate professional [[computer-aided design]] applications employed in the fields of architecture, machining, engineering, simulations, and similar fields.<ref>{{cite web| url = http://www.motherboards.org/files/techspecs/apro_r11a.pdf| title = AGP Pro 1.1a specification}}</ref>

====64-bit AGP====
A [[64-bit computing|64-bit]] channel was once proposed as an optional standard for AGP 3.0 in draft documents,<ref>{{cite web |url = http://www.intel.com/technology/agp/downloads/agp8x_v091R_042401.pdf |title = Draft AGP8× Interface Specification Rev. 0.91R |archive-url=https://web.archive.org/web/20010613041316/http://www.intel.com/technology/agp/downloads/agp8x_v091R_042401.pdf |archive-date=13 June 2001 |url-status=dead}}</ref> but it was dropped in the final version of the standard.

The standard allows 64-bit transfer for AGP8× reads, writes, and fast writes; 32-bit transfer for PCI operations.

===Unofficial variations===
A number of non-standard variations of the AGP interface have been produced by manufacturers.

====Internal AGP interface====
;Ultra-AGP, Ultra-AGPII: It is an internal AGP interface standard used by [[Silicon Integrated Systems|SiS]] for the north bridge controllers with integrated graphics. The original version supports same bandwidth as AGP 8×, while Ultra-AGPII has maximum 3.2&nbsp;GB/s bandwidth.

====PCI-based AGP ports====
;AGP Express: Not a true AGP interface, but allows an AGP card to be connected over the legacy [[Peripheral Component Interconnect|PCI bus]] on a [[PCI Express]] motherboard. It is a technology used on motherboards made by [[Elitegroup Computer Systems|ECS]], intended to allow an existing AGP card to be used in a new motherboard instead of requiring a PCIe card to be obtained (since the introduction of PCIe graphics cards few motherboards provide AGP slots). An "AGP Express" slot is basically a PCI slot (with twice the electrical power) with an AGP connector. It offers backward compatibility with AGP cards, but provides incomplete support<ref>{{cite web|url=http://www.ecs.com.tw/ECSWeb/Support/agp.aspx?MenuID=0&LanID=0 |archive-url=https://web.archive.org/web/20051216142008/http://www.ecs.com.tw/ECSWeb/Support/agp.aspx?MenuID=0&LanID=0 |url-status=dead |archive-date=16 December 2005 |title=ECS Web Site |access-date=15 September 2014 }}</ref> (some AGP cards do not work with AGP Express) and reduced performance—the card is forced to use the shared PCI bus at its lower bandwidth, rather than having exclusive use of the faster AGP.
;AGI: The ASRock Graphics Interface (AGI) is a proprietary variant of the Accelerated Graphics Port (AGP) standard. Its purpose is to provide AGP-support for ASRock motherboards that use chipsets lacking native AGP support. However, it is not fully compatible with AGP, and several video card chipsets are known not to be supported.
;AGX: The [[EPoX]] Advanced Graphics eXtended (AGX) is another proprietary AGP variant with the same advantages and disadvantages as AGI. User manuals recommend not using AGP 8× ATI cards with AGX slots.
;XGP: The [[Biostar]] Xtreme Graphics Port is another AGP variant, also with the same advantages and disadvantages as AGI and AGX.

====PCIe based AGP ports====
;AGR: The [[Advanced Graphics Riser]] is a variation of the AGP port used in some PCIe motherboards made by [[Micro-Star International|MSI]] to offer limited backward compatibility with AGP. It is, effectively, a modified PCIe slot allowing for performance comparable to an AGP 4×/8× slot,<ref>{{cite web |url=http://www.pcstats.com/articleview.cfm?articleid=1806&page=2 |title=MSI K8N Neo3-F Motherboard Review—What's an AGR video slot? |access-date=15 September 2014 |archive-url=https://web.archive.org/web/20141110101536/http://www.pcstats.com/articleview.cfm?articleid=1806&page=2 |archive-date=10 November 2014 |url-status=dead }}</ref> but does not support all AGP cards; the manufacturer published a list of some cards and chipsets that work with the modified slot.<ref>{{cite web|url=http://www.msi.com.tw/html/products/mainboard/agr/7135agr.pdf |title=List of cards and chipsets that work with the MSI AGR port |access-date=15 September 2014 |url-status=dead |archive-url=https://web.archive.org/web/20070308180139/http://www.msi.com.tw/html/products/mainboard/agr/7135agr.pdf |archive-date=March 8, 2007 }}</ref>