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'''Accelerated Graphics Port''' ('''AGP''') is a [[parallel communication|parallel]] [[expansion card]] standard, designed for attaching a [[video card]] to a [[computer]] system to assist in the acceleration of [[3D computer graphics]]. It was originally designed as a successor to [[Peripheral Component Interconnect|PCI]]-type connections for video cards. Since 2004, AGP was progressively phased out in favor of [[PCI Express]] (PCIe), which is [[serial communication|serial]], as opposed to parallel; by mid-2008, PCI Express cards dominated the market and only a few AGP models were available,<ref>{{cite web |url=http://news.softpedia.com/news/AGP-Almost-at-the-End-of-the-Road-87316.shtml |title=AGP almost at the end, Softpedia |date=5 June 2008 |access-date=15 September 2014 |archive-url=https://web.archive.org/web/20141023222525/http://news.softpedia.com/news/AGP-Almost-at-the-End-of-the-Road-87316.shtml |archive-date=23 October 2014 |url-status=dead }}</ref> with GPU manufacturers and add-in board partners eventually dropping support for the interface in favor of PCI Express.
'''Accelerated Graphics Port''' ('''AGP''') is an [[Obsolescence#Technical obsolescence|obsolete]] [[parallel communication|parallel]] [[expansion card]] standard, designed by [[Intel]] independently of the [[PCI-SIG]] for attaching a [[video card]] to a [[computer]] system to assist in the acceleration of [[3D computer graphics]]. It was originally designed as a generally compatible successor to [[Peripheral Component Interconnect|PCI]]-type connections for video cards. The AGP bus was separate from the PCI bus, so that the graphics card as the top consumer of bandwidth in a computer system would not have to compete for bandwidth with other [[Expansion card|devices]], while the overall throughput of the system was greatly increased by the addition of another data bus. The separation also allowed for improvements that broke compatibility with the myriad of existing PCI cards and AGP was not required to be a lowest common denominator standard. The introduction of more efficient{{efn|provided that many transactions can be started in parallel and the penalty of increased latency per transaction is negligible, both of which are true for memory access patterns exhibited by graphics cards}} queued transactions on top of PCI made it possible for the graphics card to [[Direct memory access|use system memory directly]] in many circumstances where regular PCI cards required local copies of the data. Since 2004, AGP and PCI were progressively phased out in favor of [[PCI Express]] (PCIe). By mid-2008, PCI Express cards dominated the market and only a few AGP models were available,<ref>{{cite web |url=http://news.softpedia.com/news/AGP-Almost-at-the-End-of-the-Road-87316.shtml |title=AGP almost at the end, Softpedia |date=5 June 2008 |access-date=15 September 2014 |archive-url=https://web.archive.org/web/20141023222525/http://news.softpedia.com/news/AGP-Almost-at-the-End-of-the-Road-87316.shtml |archive-date=23 October 2014 |url-status=dead }}</ref> with GPU manufacturers and add-in board partners eventually dropping support for the interface relatively quickly in favor of PCI Express. The analogue of AGP in [[Industry Standard Architecture|ISA]] bus systems was the [[VESA Local Bus]].


=={{Anchor|APERTURE}}Advantages over PCI==
=={{Anchor|APERTURE}}Advantages over PCI==
AGP is a superset of the PCI standard, designed to overcome PCI's limitations in serving the requirements of the era's high-performance graphics cards.<ref>{{Cite web |last=By |date=2024-03-03 |title=A Better Use For The AGP Slot, Decades Later |url=https://hackaday.com/2024/03/03/a-better-use-for-the-agp-slot-decades-later/ |access-date=2024-11-11 |website=Hackaday |language=en-US}}</ref>
AGP is a superset of the PCI standard, designed to overcome PCI's limitations in serving the requirements of the era's high-performance graphics cards.<ref>{{Cite web |last=By |date=2024-03-03 |title=A Better Use For The AGP Slot, Decades Later |url=https://hackaday.com/2024/03/03/a-better-use-for-the-agp-slot-decades-later/ |access-date=2024-11-11 |website=Hackaday |language=en-US}}</ref>


The primary advantage of AGP is that it doesn't share the PCI [[Bus (computing)|bus]], providing a dedicated, [[Point-to-point (telecommunications)|point-to-point]] pathway between the expansion slot(s) and the motherboard chipset. The direct connection also allows higher clock speeds.
The primary advantage of AGP is its independence from the PCI [[Bus (computing)|bus]], providing a dedicated, [[Point-to-point (telecommunications)|point-to-point]] pathway between the expansion slot(s) and the motherboard chipset. The direct connection also allows backward-incompatible changes such as a lower signal voltage, which in turn allows a higher clock speed.


The second major change is the use of split [[Peripheral Component Interconnect#PCI bus transactions|transactions]], wherein the address and data phases are separated. The card may send many address phases, so the host can process them in order, avoiding any long delays caused by the bus being idle during read operations.
The second major change is the use of split [[Peripheral Component Interconnect#PCI bus transactions|transactions]], wherein the address and data phases (request and response phases) are separated. More than one transaction can be in-flight. This allows READ transactions to perform equally well to WRITE transactions, which is hard to achieve with just strictly serial transaction processing where the bus must remain idle (in a wait state) while waiting for the read data access to finish (on the other hand, with or without queues, a "fire and forget" write transaction can be complete when it is received and before the actual memory write completes). With AGP's queued transactions, the bandwidth realized can be close to the theoretical maximum bandwidth. AGP has a high priority queue and a low priority queue to allow for fine-grained optimization.<ref name="spec2.0">AGP Specification 2.0</ref>{{rp|26}} This great improvement in memory read performance makes it practical for an AGP card to read [[Texture mapping|textures]] directly from system RAM, while a PCI graphics card must copy it from system RAM to the card's [[video memory]]. System memory is made available using the [[graphics address remapping table]] (GART), which apportions main memory as needed for texture storage.<ref>{{cite web |url=http://www.sysopt.com/features/mboard/article.php/3549951 |title=What is AGP? |access-date=15 September 2014 |url-status=dead |archive-url=https://web.archive.org/web/20120509222057/http://www.sysopt.com/features/mboard/article.php/3549951 |archive-date=9 May 2012 }}</ref> The maximum amount of system memory available to AGP is defined as the ''AGP [[Aperture (computer memory)|aperture]]''. Thus a trade-off could be realized in which the newly gained bandwidth could be exchanged for a lower parts count (graphics cards with little or no onboard memory).


Third, PCI bus handshaking is simplified. Unlike PCI bus transactions, whose length is negotiated on a cycle-by-cycle basis using the FRAME# and STOP# signals, AGP transfers are always a multiple of 8&nbsp;bytes long, with the total length included in the request. Further, rather than using the IRDY# and TRDY# signals for each word, data is transferred in blocks of 4&nbsp;clock cycles (32&nbsp;words at AGP 8× speed), and pauses are allowed only between blocks.
Third, AGP allows (mandatory only in AGP 3.0) ''sideband addressing'', meaning that the [[address bus|address]] and data buses are separated, so the address phase does not use the main address/data (AD) lines at all. This is done by adding an extra 8-bit "SideBand Address" [[computer bus|bus]], over which the graphics controller can issue new AGP requests while other AGP data is flowing over the main 32 address/data (AD) lines. This results in improved overall AGP data throughput.


Finally, AGP allows (mandatory only in AGP 3.0) ''sideband addressing'', meaning that the [[address bus|address]] and data buses are separated, so the address phase does not use the main address/data (AD) lines at all. This is done by adding an extra 8-bit "SideBand Address" [[computer bus|bus]], over which the graphics controller can issue new AGP requests while other AGP data is flowing over the main 32 address/data (AD) lines. This results in improved overall AGP data throughput.
Finally, PCI bus handshaking is simplified. Unlike PCI bus transactions, whose length is negotiated on a cycle-by-cycle basis using the FRAME# and STOP# signals, AGP transfers are always a multiple of 8&nbsp;bytes long, with the total length included in the request. Further, rather than using the IRDY# and TRDY# signals for each word, data is transferred in blocks of 4&nbsp;clock cycles (32&nbsp;words at AGP 8× speed), and pauses are allowed only between blocks.
 
This great improvement in memory read performance makes it practical for an AGP card to read [[Texture mapping|textures]] directly from system RAM, while a PCI graphics card must copy it from system RAM to the card's [[video memory]]. System memory is made available using the [[graphics address remapping table]] (GART), which apportions main memory as needed for texture storage.<ref>{{cite web |url=http://www.sysopt.com/features/mboard/article.php/3549951 |title=What is AGP? |access-date=15 September 2014 |url-status=dead |archive-url=https://web.archive.org/web/20120509222057/http://www.sysopt.com/features/mboard/article.php/3549951 |archive-date=9 May 2012 }}</ref> The maximum amount of system memory available to AGP is defined as the ''AGP [[Aperture (computer memory)|aperture]]''.


==History==
==History==
[[Image:AGP-Video-Card.jpg|thumb|An AGP card]]
[[Image:AGP-Video-Card.jpg|thumb|An AGP card]]


The AGP slot first appeared on [[x86]]-compatible system boards based on [[Socket 7]] Intel [[P5 (microarchitecture)|P5]] [[Pentium]] and [[Slot 1]] [[P6 (microarchitecture)|P6]] [[Pentium II]] processors. Intel introduced AGP support with the i[[440LX]] Slot 1 chipset on August 26, 1997, and a flood of products followed from all the major system board vendors.<ref name=Intel440LXdata>{{cite web |url=http://www.intel.com/design/chipsets/datashts/290564.htm |title=Intel 440LX AGPset |access-date=15 September 2014}}</ref>
The AGP slot first appeared on [[x86]]-compatible system boards based on [[Socket 7]] Intel [[P5 (microarchitecture)|P5]] [[Pentium]] and [[Slot 1]] [[P6 (microarchitecture)|P6]] [[Pentium II]] processors. Intel introduced AGP support with the i[[440LX]] Slot 1 chipset on August 26, 1997, and a flood of products followed from all the major system board vendors.<ref name=Intel440LXdata>{{cite web |url=http://www.intel.com/design/chipsets/datashts/290564.htm |title=Intel 440LX AGPset |access-date=15 September 2014}}</ref> AGP was developed by Intel independently of the [[PCI-SIG|PCI Special Interest Group]], which neither reviewed nor endorsed it.<ref name="spec2.0"/>{{rp|20}}


The first Socket 7 chipsets to support AGP were the [[VIA Technologies|VIA]] [[Apollo VP3]], [[Silicon Integrated Systems|SiS]] 5591/5592, and the [[Acer Laboratories Incorporated|ALI]] Aladdin V. Intel never released an AGP-equipped Socket 7 chipset. [[First International Computer|FIC]] demonstrated the first Socket 7 AGP system board in November 1997 as the ''FIC PA-2012'' based on the VIA Apollo VP3 chipset, followed very quickly by the ''EPoX P55-VP3'' also based on the VIA VP3 chipset which was first to market.<ref>{{cite web |author=Lal Shimpi, Anand |url=http://www.anandtech.com/showdoc.aspx?i=155&p=1 |title=Chipset Guide |publisher=AnandTech |date=August 1, 1997 |access-date=2015-03-03}}</ref>
The first Socket 7 chipsets to support AGP were the [[VIA Technologies|VIA]] [[Apollo VP3]], [[Silicon Integrated Systems|SiS]] 5591/5592, and the [[Acer Laboratories Incorporated|ALI]] Aladdin V. Intel never released an AGP-equipped Socket 7 chipset. [[First International Computer|FIC]] demonstrated the first Socket 7 AGP system board in November 1997 as the ''FIC PA-2012'' based on the VIA Apollo VP3 chipset, followed very quickly by the ''EPoX P55-VP3'' also based on the VIA VP3 chipset which was first to market.<ref>{{cite web |author=Lal Shimpi, Anand |url=http://www.anandtech.com/showdoc.aspx?i=155&p=1 |archive-url=https://web.archive.org/web/20071208073030/http://anandtech.com/showdoc.aspx?i=155&p=1 |url-status=dead |archive-date=December 8, 2007 |title=Chipset Guide |publisher=AnandTech |date=August 1, 1997 |access-date=2015-03-03}}</ref>


Early video chipsets featuring AGP support included the [[Rendition (company)|Rendition]] Vérité V2200, [[3dfx]] [[3dfx#Voodoo Banshee|Voodoo Banshee]], [[Nvidia]] [[RIVA 128]], [[3Dlabs]] PERMEDIA 2, [[Intel740|Intel i740]], [[ATI Rage|ATI Rage series]], [[Matrox]] Millennium II, and [[S3 ViRGE|S3 ViRGE GX/2]]. Some early AGP boards used graphics processors built around PCI and were simply bridged to AGP. This resulted in the cards benefiting little from the new bus, with the only improvement used being the 66&nbsp;MHz bus clock, with its resulting doubled bandwidth over PCI, and bus exclusivity. Intel's i740 was explicitly designed to exploit the new AGP feature set; in fact it was designed to texture only from AGP memory, making PCI versions of the board difficult to implement (local board RAM had to emulate AGP memory), though this was eventually accomplished much later in the form of AGP-to-PCI bridges.
Early video chipsets featuring AGP support included the [[Rendition (company)|Rendition]] Vérité V2200, [[3dfx]] [[3dfx#Voodoo Banshee|Voodoo Banshee]], [[Nvidia]] [[RIVA 128]], [[3Dlabs]] PERMEDIA 2, [[Intel740|Intel i740]], [[ATI Rage|ATI Rage series]], [[Matrox]] Millennium II, and [[S3 ViRGE|S3 ViRGE GX/2]]. Some early AGP boards used graphics processors built around PCI and were simply bridged to AGP. This resulted in the cards benefiting little from the new bus, with the only improvement used being the 66&nbsp;MHz bus clock, with its resulting doubled bandwidth over PCI, and bus exclusivity. Intel's i740 was explicitly designed to exploit the new AGP feature set; in fact it was designed to texture only from AGP memory, making PCI versions of the board difficult to implement (local board RAM had to emulate AGP memory), though this was eventually accomplished much later in the form of AGP-to-PCI bridges.
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|AGP 2.0 || 1.5&nbsp;V || 66&nbsp;MHz || {{0}}4× || {{0|000}}4 || 1066
|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 3.0 || rowspan=2 | 0.8&nbsp;V || rowspan=2 | 66&nbsp;MHz || rowspan=2 | {{0}}8× || rowspan=2 | {{0|000}}8 || rowspan=2 | 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>
|-
|-
|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>
|AGP 3.5{{efn|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.}}
|}
|}


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.)
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.
There are various physical interfaces (connectors); see the [[#Compatibility|Compatibility]] section.
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;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.
;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====
====PCI-based AGP slots====
;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.
;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.
;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.
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;XGP: The [[Biostar]] Xtreme Graphics Port is another AGP variant, also with the same advantages and disadvantages as AGI and AGX.
;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====
====PCIe-based AGP slots====
;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>
;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>


==Compatibility==
==Compatibility==
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AGP cards are [[Backward compatibility|backward]] and [[Forward compatibility|forward compatible]] within limits. 1.5 V-only keyed cards will not go into 3.3 V slots and vice versa, though "Universal" cards exist which will fit into either type of slot. There are also unkeyed "Universal" slots that will accept either type of card. When an AGP Universal card is plugged-into an AGP Universal slot, only the 1.5 V portion of the card is used. Some cards, like Nvidia's [[GeForce 6]] series (except the 6200) or ATI's [[Radeon X800]] series, only have keys for 1.5 V to prevent them from being installed in older mainboards without 1.5 V support. Some of the last modern cards with 3.3 V support were:
AGP cards are [[Backward compatibility|backward]] and [[Forward compatibility|forward compatible]] within limits. 1.5 V-only keyed cards will not go into 3.3 V slots and vice versa, though "Universal" cards exist which will fit into either type of slot. There are also unkeyed "Universal" slots that will accept either type of card. When an AGP Universal card is plugged-into an AGP Universal slot, only the 1.5 V portion of the card is used. Some cards, like Nvidia's [[GeForce 6]] series (except the 6200) or ATI's [[Radeon X800]] series, only have keys for 1.5 V to prevent them from being installed in older mainboards without 1.5 V support. Some of the last modern cards with 3.3 V support were:
* the Nvidia [[GeForce FX]] series (FX 5200, FX 5500, FX 5700, some FX 5800, FX 5900 and some FX 5950),
* the Nvidia [[GeForce FX]] series (FX 5200, FX 5500, FX 5600, FX 5700, some FX 5800, FX 5900 and some FX 5950),
* certain Nvidia [[GeForce 6 series]] and [[GeForce 7 series|7 series]] (some 6600, 6800, 7300, 7600, 7800, 7900 and 7950 cards, really uncommon compared to their AGP 1.5v only versions; the GeForce 6200 is the only exception, as it was the most common card with 3.3 V support),
* certain Nvidia [[GeForce 6 series]] and [[GeForce 7 series|7 series]] (some 6600, 6800, 7300, 7600, 7800, 7900 and 7950 cards, really uncommon compared to their AGP 1.5v only versions; the GeForce 6200 is the only exception, as it was the most common card with 3.3 V support),
* the ATI [[Radeon 9000 series]] ([[Radeon R300|Radeon 9500/9700/9800 (R300/R350)]], but not 9600/9800 (R360/RV360)).
* the ATI [[Radeon 9000 series]] ([[Radeon R300|Radeon 9500/9700/9800 (R300/R350)]], but not 9600/9800 (R360/RV360)).
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