Editing Accelerated Graphics Port (section)

==Compatibility==
[[Image:AGP & AGP Pro Keying.svg|right|thumb|300px|Compatibility, AGP Keys on card (top), on slot (bottom)]]

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),
* 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)).

Some cards incorrectly have dual notches, and some motherboards incorrectly have fully open slots, allowing a card to be plugged into a slot that does not support the correct signaling voltage, which may damage card or motherboard. Some incorrectly designed older 3.3 V cards have the 1.5 V key.

AGP Pro cards will not fit into standard slots, but standard AGP cards will work in a Pro slot. Motherboards equipped with a Universal AGP Pro slot will accept a 1.5 V or 3.3 V card in either the AGP Pro or standard AGP configuration, a Universal AGP card, or a Universal AGP Pro card.

There are some proprietary systems incompatible with standard AGP; for example, [[Apple Computer|Apple]] [[Power Macintosh]] computers with the [[Apple Display Connector]] (ADC) have an extra connector which delivers power to the attached display. Some cards designed to work with a specific [[CPU design|CPU architecture]] (e.g., PC, Apple) may not work with others due to [[firmware]] issues.

Mark Allen of Playtools.com has made the following comments regarding practical AGP compatibility for AGP 3.0 and AGP 2.0: {{blockquote|...&nbsp;nobody makes AGP 3.0 cards, and nobody makes AGP 3.0 motherboards. At least not any manufacturers I can find. Every single video card I could find which claimed to be an AGP 3.0 card was actually a universal 1.5V AGP 3.0 card. And every motherboard which claimed to be an AGP 3.0 motherboard turned out to be a universal 1.5V AGP 3.0 motherboard. It makes sense, if you think about it, because if anyone actually shipped a consumer-oriented product which supported only 0.8 volts, they would end up with lots of confused customers and a support nightmare. In the consumer market, you'd have to be crazy to ship a 0.8 volt only product.<ref>{{cite web|last1=Allen|first1=Mark|title=AGP compatibility for sticklers|work=Video card information|url=http://www.playtool.com/pages/agpcompat/agp.html|publisher=PlayTool.com|archive-url=https://web.archive.org/web/20160622083724/http://www.playtool.com/pages/agpcompat/agp.html|archive-date=22 June 2016|year=2006}}</ref>}}