Agp Universal Slot



Version 2.0 of AGP was powered by 1.5 V, and AGP 2.0 'universal' connectors which could support either voltage were released. AGP version 3.0, released in 2002, doubled the speed of AGP 2.0 with a new AGP 8x mode.

  • The AGP slots In fig 1.1 is a typical AGP Pro Universal slot on a motherboard. We have pointed out the alignment keys, which, in conjunction with the alignment notches on the AGP/AGP Pro video card ensures the card is installed correctly. The two extensions we have pointed out are used to provide extra power to the AGP Pro cards.
  • AGP: This type of expansion slot was specifically designed to deal with graphics adapters. In fact, AGP stands for Accelerated Graphics Port.Older PCs may sport this expansion slot, but the best video cards use PCI Express.

AGP Compatibility: The Short Version

If an AGP card fits in an AGP expansion slot then they are compatible. But read the rest of this anyway. There are some rare exceptions where motherboard and video card manufacturers don't obey the rules.

AGP Compatibility: The Long Version

AGP Basics

In 1996, Intel introduced AGP 1.0. AGP was a modified version of PCI designed to speed up transfers to video cards. It was followed by AGP 2.0 in 1998 and AGP 3.0 in 2002. Each new version added new speeds and signaling voltages.

AGP VersionSignaling VoltagePeak Speeds
AGP 1.0 3.3 Volts1X at 267MB/s, 2X at 533MB/s
AGP 2.0 1.5 Volts1X at 267MB/s, 2X at 533MB/s, 4X at 1067MB/s
AGP 3.0 0.8 Volts4X at 1067MB/s, 8X at 2133MB/s

The signaling voltage is the voltage used to send data between the AGP card and the AGP motherboard. You can download the final AGP 3.0 specification from here. You may also want to look at the AGP 2.0 specification and the AGP Pro 1.1a specification.

AGP Connectors And Slots

Each AGP card has one or two slots in its card edge. If a video card has the 3.3 volt slot, then it can use 3.3 volt signaling. AGP 2.0 added the 1.5 volt slot on cards which could use 1.5 volt signaling. If the card has both slots then it can use both signaling voltages. AGP 3.0 added support for 0.8 volt signaling but it did not add a new kind of slot. If a video card supports either 1.5 volt or 0.8 volt signaling then it has the 1.5 volt slot.

Agp universal slot machines

The AGP connectors on the motherboard are keyed to prevent insertion of AGP cards which would be damaged if plugged in. An AGP 3.3V motherboard connector can only accept AGP cards which have the 3.3V slot. If you try to insert a card without a 3.3V slot into an AGP 3.3V motherboard connector, the card will bump into the connector key and cannot be inserted. Likewise an AGP 1.5V motherboard connector can only accept AGP cards with the 1.5V slot. An AGP universal motherboard connector has no keys and therefore can accept any kind of AGP card. An AGP card with both voltage slots can be plugged into any kind of AGP motherboard connector. If you can plug an AGP card into an AGP motherboard connector, then neither the card nor the motherboard will be damaged (assuming they obey the AGP specifications).

AGP Pro motherboard connectors were created to support video cards which use more power than a plain AGP connector can supply. There are extra connectors on both ends of an AGP Pro motherboard connector which allow an AGP Pro video card to draw more power. Plain AGP cards are fully compatible with AGP Pro motherboards, but it doesn't work the other way around. AGP motherboards are not compatible with AGP Pro video cards. High-end motherboards are often actually AGP Pro motherboards because they can accept both AGP cards and AGP Pro cards. But AGP Pro video cards are rarely seen outside the workstation market because they aren't compatible with AGP motherboards. Consumer-oriented video cards which need to draw lots of power usually require you to plug in a disk drive power supply cable. That way they can be compatible with all motherboards and still use lots of power.

Official AGP Compatibility

Graphics Card Types (table 16 from the AGP 3.0 specification)
Graphics Card TypesConnector Type Description
AGP 3.3V Card3.3V slotSupports only 3.3V signaling. Available speeds 1x, 2x.
AGP 1.5V Card1.5V slotSupports only 1.5V signaling. Available speeds 1x, 2x, 4x.
Universal AGP CardDouble slottedSupports 3.3V and 1.5V signaling. Available speeds 1x, 2x at 3.3V and 1x, 2x, 4x at 1.5V.
AGP 3.0 Card1.5V slotSupports only 0.8V signaling. Available speeds 4x, 8x.
Universal 1.5V AGP 3.0 Card1.5V slotSupports 1.5V and 0.8V signaling. Available speeds 1x, 2x, 4x at 1.5V and 4x, 8x at 0.8V.
Universal AGP 3.0 CardDouble slottedSupports AGP 3.3v, 1.5V, and 0.8V signaling. Available speeds 1x, 2x at 3.3V and 1x, 2x, 4x at 1.5V and 4x, 8x at 0.8V.

The table above gives Intel's official names for the various kinds of AGP cards allowed by the AGP specifications. Unfortunately, the technical specifications for a video card rarely use these terms properly (if at all) to describe the video card. They usually just list the fastest AGP multipliers it supports: '8X, 4X', or '4X'. From that information and the voltage slots on a picture of the video card, you can often figure out exactly what it is. I've seen plenty of video cards listed as 'AGP 3.0 cards' when in fact they are actually Universal 1.5V AGP 3.0 cards. I've also seen cards listed as 'AGP 8X,4X 1.5 volt only' when there is really no such thing. What they are trying to tell you is that it's a Universal 1.5V AGP 3.0 Card and doesn't support 3.3 volts. It is required to support 0.8 volts if it supports 8X.

Motherboard Types (table 15 from the AGP 3.0 specification)
Motherboard TypesConnector Type Description
AGP 3.3V Motherboard3.3V keyedSupports only 3.3V signaling. Available speeds 1x, 2x.
AGP 1.5V Motherboard1.5V keyedSupports only 1.5V signaling. Available speeds 1x, 2x, 4x.
Universal AGP MotherboardUniversalSupports both 3.3V and 1.5V signaling. Available speeds 1x, 2x at 3.3V and 1x, 2x, 4x at 1.5V.
AGP 3.0 Motherboard1.5V keyedSupports only 0.8V signaling. Additional electrical ID to prevent 1.5V operation. Available speeds 4x, 8x.
Universal 1.5V AGP 3.0 Motherboard1.5V keyedSupports 1.5V and 0.8V signaling. Available speeds 1x, 2x, 4x at 1.5V and 4x, 8x at 0.8V.
Universal AGP 3.0 MotherboardUniversalSupports 3.3V, 1.5V, and 0.8V signaling. Available speeds 1x, 2x at 3.3V and 1x, 2x, 4x at 1.5V and 4x, 8x at 0.8V.

The table above gives Intel's official names for the various kinds of AGP motherboards allowed by the AGP specifications. The technical specifications for motherboards tend to be just as sloppy as they are for video cards. Sometimes they use the official motherboard type names properly and sometimes they do not.

Motherboard And Card Compatibility (table 35 from the AGP 3.0 specification)
AGP 3.3V CardAGP 1.5V CardUniversal AGP CardAGP 3.0 CardUniversal 1.5V AGP 3.0 CardUniversal AGP 3.0 Card
AGP 3.3V MotherboardWorks at 3.3VWon't fit in slotWorks at 3.3VWon't fit in slotWon't fit in slotWorks at 3.3V
AGP 1.5V MotherboardWon't fit in slotWorks at 1.5VWorks at 1.5VFits in slot but won't work.Works at 1.5VWorks at 1.5V
Universal AGP MotherboardWorks at 3.3VWorks at 1.5VWorks at 1.5VFits in slot but won't workWorks at 1.5VWorks at 1.5V
AGP 3.0 MotherboardWon't fit in slotFits in slot but won't workFits in slot but won't workWorks at 0.8VWorks at 0.8VWorks at 0.8V
Universal 1.5V AGP 3.0 MotherboardWon't fit in slotWorks at 1.5VWorks at 1.5VWorks at 0.8VWorks at 0.8VWorks at 0.8V
Universal AGP 3.0 MotherboardWorks at 3.3VWorks at 1.5VWorks at 1.5VWorks at 0.8VWorks at 0.8VWorks at 0.8V

The table above shows the results of all possible combinations of AGP cards and AGP motherboards.

Practical AGP Compatibility

The previous table shows that there are combinations of motherboards and video cards which can be plugged together but do not work. According to the AGP specifications there should be no damage, but the combination would not be compatible. You see people posting in forums worrying about this possibility all the time. There are also stories that you can get some 0.8 volt only cards which are willing to tolerate 1.5 volts but that you really shouldn't plug them into an AGP 4X motherboard even if they work. Given the previous table, the confusion is understandable. But there are two pieces of information which they're missing: 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 your 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. And as far as I can tell, there aren't any in the workstation market either. There may be some obscure product somewhere, but I sure can't find any. It's easy to find ones which are mislabeled as AGP 3.0 cards or motherboards but I haven't been able to find the actual item. If you remove the 0.8 volt only entries from the compatibility table, then you end up with the following table.

Practical Motherboard And Card Compatibility
AGP 3.3V CardAGP 1.5V CardUniversal AGP CardUniversal 1.5V AGP 3.0 CardUniversal AGP 3.0 Card
AGP 3.3V MotherboardWorks at 3.3VWon't fit in slotWorks at 3.3VWon't fit in slotWorks at 3.3V
AGP 1.5V MotherboardWon't fit in slotWorks at 1.5VWorks at 1.5VWorks at 1.5VWorks at 1.5V
Universal AGP MotherboardWorks at 3.3VWorks at 1.5VWorks at 1.5VWorks at 1.5VWorks at 1.5V
Universal 1.5V AGP 3.0 MotherboardWon't fit in slotWorks at 1.5VWorks at 1.5VWorks at 0.8VWorks at 0.8V
Universal AGP 3.0 MotherboardWorks at 3.3VWorks at 1.5VWorks at 1.5VWorks at 0.8VWorks at 0.8V

That's why 'If an AGP card fits in an AGP slot then they are compatible' is actually correct if you only consider stuff you can really buy.

Agp universal slots

One practical matter which must be considered is the fact that some of the original AGP 1.0 motherboards do not provide enough power to operate some newer AGP video cards reliably. For example, some of the original motherboards using the first chipsets which supported AGP (like the Intel 440LX and 440BX) can become unstable if you install video cards which draw lots of power through the AGP slot. The motherboards can't always supply the necessary current for the newer video cards. So if you're adding a video card to an AGP 1.0 motherboard then it's a good idea to install a video card which doesn't consume very much power.

You can also occasionally get memory resource conflicts by installing a new AGP video card into an old AGP 1.0 motherboard. The video card will work properly until you install the display driver. Once you try to install the driver, a memory conflict shows up. The range of conflicting addresses varies from case to case. This problem is very unusual and when it happens it is rarely possible to fix it. I'm not sure exactly what causes the problem but apparently the motherboard and the video card are incompatible in some way which prevents Windows from properly assigning memory addresses to the video card. In the cases I've seen, there doesn't seem to be any way to predict from the video card chipset and motherboard chipset whether there will be a problem. Sometimes a particular video card chipset and motherboard chipset get along well and other times they don't. I'd guess that it's some kind of incompatibility caused by an outdated motherboard BIOS and possibly the video card BIOS. The one thing you can try is to flash your motherboard with the most recent BIOS. But since it's an old motherboard, the manufacturer will most likely not have anything but old BIOSes available. If you're running Windows 95, 98, or ME, it may be possible to manually assign addresses and get it to work but I've seen people try this and the process is about as enjoyable as a root canal and usually fails to fully solve the problem anyway. If you're running Windows 2000 or XP then it's probably impossible to fix because the newer versions of Windows almost always prevent you from manually assigning addresses, IRQs, etc. That's almost always true even if you select the standard PC HAL while installing Windows with the hope that it will allow you to assign resources manually. If you run into one of these memory resource conflicts then you should probably give up and try a different video card. It's rarely fixable.

AGP Cards

The table below lists the AGP graphics card type for just about all of the consumer-oriented AGP graphics cards. Note the complete lack of 'AGP 3.0 Card' entries. The graphics chipset determines what kind of AGP card it is; not the brand of the video card. If you would like to know what kind of video card is in your computer, open the 'Control Panel' and double-click 'Display' to bring up the 'Display Properties' window. Then select the 'Settings' tab, click 'Advanced', and select the 'Adapter' tab. Sandra Lite can also give you very detailed information about your display adapter.

Sometimes manufacturers don't obey the rules. I found a video card which had incorrect voltage slots. It had only a 3.3 volt slot when in fact the video card could also have accepted 1.5 volts. That card would work correctly in an AGP 3.3V motherboard but it also would have worked in a 1.5 volt motherboard had it been given the 1.5 volt slot. There also was a SiS video card manufactured years ago which had the wrong voltage slots. If you plugged it into the wrong motherboard, it would be destroyed. The 'wrong slots' case used to be extremely rare and any manufacturer which made that mistake quickly acquired a very bad reputation. Unfortunately building AGP video cards with the wrong voltage slots is becoming more common. It's not difficult to find no-name, low-budget, Chinese video cards on EBAY which have the 3.3 volt slot despite the fact that the graphics chipset does not support 3.3 volts. It pays to stick with competent manufacturers. As long as they obey the AGP spec, you cannot damage anything by plugging a video card into a motherboard.

AgpAgp
Graphics CardGraphics Card Type
ATI FireGL 1AGP 3.3V Card
ATI FireGL 2Universal AGP Card
ATI FireGL 3Universal AGP Card
ATI FireGL 4Universal AGP Card
ATI FireGL 8700Universal AGP Card
ATI FireGL 8800Universal AGP Card
ATI FireGL T2Universal 1.5V AGP 3.0 Card
ATI FireGL X1Universal 1.5V AGP 3.0 Card
ATI FireGL X1-256pUniversal 1.5V AGP 3.0 Card
ATI FireGL X2-256tUniversal 1.5V AGP 3.0 Card
ATI FireGL Z1Universal 1.5V AGP 3.0 Card
ATI Radeon Mac EditionUniversal AGP Card?
ATI Radeon (Radeon 32, Radeon 64, All In Wonder Radeon)Universal AGP Card
ATI Radeon VEUniversal AGP Card
ATI Radeon 7000Universal AGP Card
ATI Radeon 7200Universal AGP Card
ATI Radeon 7500Universal AGP Card
ATI Radeon 8500Universal AGP Card
ATI Radeon 9000Universal AGP Card
ATI Radeon 9200Universal AGP 3.0 Card
ATI Radeon 9250Universal AGP 3.0 Card
ATI Radeon 9500Universal AGP 3.0 Card
ATI Radeon 9550Universal 1.5V AGP 3.0 Card
ATI Radeon 9600Universal 1.5V AGP 3.0 Card
ATI Radeon 9700Universal AGP 3.0 Card
ATI Radeon 9800Universal 1.5V AGP 3.0 Card orUniversal AGP 3.0 Card
ATI Radeon X800Universal 1.5V AGP 3.0 Card
ATI Radeon X850Universal 1.5V AGP 3.0 Card
ATI Rage 128 (Xpert 99, Xpert 128, Xpert 2000, All In Wonder 128, Rage Fury, Rage Magnum)AGP 3.3V Card
ATI Rage 128 Pro (Xpert 2000 Pro, Rage Fury Pro, All In Wonder 128 Pro)Universal AGP Card
ATI Rage Fury MaxAGP 3.3V Card
ATI Rage LT Pro (Xpert LCD)AGP 3.3V Card
ATI Rage Pro (Xpert 98, Xpert XL, All In Wonder Pro, Turbo)AGP 3.3V Card
Matrox G200AGP 3.3V Card
Matrox G400Universal AGP Card orAGP 3.3V Card
Matrox G450Universal AGP Card
Matrox G550Universal AGP Card
Matrox P650Universal 1.5V AGP 3.0 Card
Matrox P750Universal 1.5V AGP 3.0 Card
Matrox ParheliaUniversal 1.5V AGP 3.0 Card orUniversal AGP 3.0 Card
NVIDIA GeForce 256Universal AGP Card
NVIDIA GeForce 6200Universal 1.5V AGP 3.0 Card
NVIDIA GeForce 6600Universal 1.5V AGP 3.0 Card
NVIDIA GeForce 6800Universal 1.5V AGP 3.0 Card
NVIDIA GeForce 7800 GSUniversal 1.5V AGP 3.0 Card
NVIDIA GeForce FX5200Universal AGP 3.0 Card
NVIDIA GeForce FX5500Universal AGP 3.0 Card
NVIDIA GeForce FX5600Universal AGP 3.0 Card
NVIDIA GeForce FX5700Universal AGP 3.0 Card
NVIDIA GeForce FX5800Universal AGP 3.0 Card
NVIDIA GeForce FX5900Universal AGP 3.0 Card
NVIDIA GeForce FX5950Universal AGP 3.0 Card
NVIDIA GeForce2Universal AGP Card
NVIDIA GeForce2 MX400Universal AGP Card
NVIDIA GeForce3Universal AGP Card
NVIDIA GeForce4 MX4000Universal AGP 3.0 Card
NVIDIA GeForce4 MX420Universal AGP Card
NVIDIA GeForce4 MX440Universal AGP Card
NVIDIA GeForce4 MX440-8Universal AGP 3.0 Card
NVIDIA GeForce4 MX460Universal AGP Card
NVIDIA GeForce4 Ti4200Universal AGP Card
NVIDIA GeForce4 Ti4200-8Universal AGP 3.0 Card
NVIDIA GeForce4 Ti4400Universal AGP Card
NVIDIA GeForce4 Ti4600Universal AGP Card
NVIDIA GeForce4 Ti4600-8Universal AGP 3.0 Card
NVIDIA GeForce4 Ti4800Universal AGP 3.0 Card
NVIDIA Riva 128ZXAGP 3.3V Card
NVIDIA Riva TNTAGP 3.3V Card
NVIDIA Riva TNT 2Universal AGP Card orAGP 3.3V Card

AGP Motherboards

There are a few motherboards which do not use the correct AGP connector. This AOpen AK79G Max is a universal 1.5V AGP 3.0 motherboard and yet it has an AGP universal connector which accepts 3.3 volt cards. Fortunately, it also has circuitry which prevents damage when a 3.3 volt AGP card is inserted and lights up an LED to warn you that the video card is a 3.3 volt card. I think they built the motherboard this way as a defense against video cards with incorrect voltage slots. You can't damage the motherboard or video card even if the video card has the wrong voltage slots with this kind of design.

You may also come across the occasional motherboard which has an AGP universal connector covered by a sticker which says 'do not insert 3.3 volt cards'. According to the specification, they shouldn't do that. Perhaps they didn't want to go to the trouble of keeping 1.5 volt keyed connectors in stock. It's a shame users have to be careful about this because if manufacturers obeyed the specification, it wouldn't be possible to make a mistake.

I also found a picture of a motherboard from one obscure manufacturer which had a universal AGP connector rather than the 1.5 volt keyed connector that it should have had. I doubt it had any circuitry to prevent damage if you inserted a 3.3 volt card and there was no hint that you shouldn't insert one. It's a good idea to stick with established manufacturers. But that was only one motherboard out of hundreds I've looked at. If you're buying a motherboard from someone you've never heard of, it might be a good idea to check that they've used the right AGP connector.

The table below lists the AGP motherboard type for just about all the consumer-oriented motherboard chipsets. There isn't a single 'AGP 3.0 Motherboard' chipset in the list. If you're not sure what kind of chipset is in your motherboard, then you can use CPU-Z or Sandra Lite to find out. Also remember that even if a chipset supports AGP, it doesn't mean that a motherboard using that chipset will always have an AGP slot. Some low-end motherboards using AGP chipsets leave out the AGP connector to cut costs.

Motherboard ChipsetMotherboard Kind
ALi TXPro (Aladdin IV)no AGP slot
ALi Aladdin VAGP 3.3V Motherboard
ALi MAGiK 1 (M1647)Universal AGP Motherboard
ALi M1649Universal AGP Motherboard
AMD 750 (751)AGP 3.3V Motherboard
AMD 760 (761)Universal AGP Motherboard
Intel 440BXAGP 3.3V Motherboard
Intel 440EXAGP 3.3V Motherboard
Intel 440FXno AGP slot
Intel 440GXAGP 3.3V Motherboard
Intel 440LXAGP 3.3V Motherboard
Intel 440ZXAGP 3.3V Motherboard
Intel 440ZX-66AGP 3.3V Motherboard
Intel 450GXno AGP slot
Intel 450KXno AGP slot
Intel 450NXno AGP slot
Intel 810no AGP slot
Intel 815Universal AGP Motherboard
Intel 820Universal AGP Motherboard
Intel 840Universal AGP Motherboard
Intel 845AGP 1.5V Motherboard
Intel 848Universal 1.5V AGP 3.0 Motherboard
Intel 850AGP 1.5V Motherboard
Intel 860AGP 1.5V Motherboard
Intel 865Universal 1.5V AGP 3.0 Motherboard
Intel 875Universal 1.5V AGP 3.0 Motherboard
Intel 910no AGP slot
Intel 915no AGP slot: PCI-Express
Intel 925no AGP slot: PCI-Express
Intel E7210no AGP slot
Intel E7221no AGP slot
Intel E7320no AGP slot
Intel E7500no AGP slot
Intel E7501no AGP slot
Intel E7505Universal 1.5V AGP 3.0 Motherboard
Intel E7520no AGP slot
Intel E7525no AGP slot: PCI-Express
NVIDIA NForceAGP 1.5V Motherboard
NVIDIA NForce 2Universal 1.5V AGP 3.0 Motherboard
NVIDIA NForce 3Universal 1.5V AGP 3.0 Motherboard
NVIDIA NForce 4no AGP slot: PCI-Express
SiS630Universal AGP Motherboard
SiS645Universal AGP Motherboard
SiS648Universal 1.5V AGP 3.0 Motherboard
SiS649no AGP slot: PCI-Express
SiS650Universal AGP Motherboard
SiS651Universal AGP Motherboard
SiS655Universal 1.5V AGP 3.0 Motherboard
SiS656no AGP slot: PCI-Express
SiS661Universal 1.5V AGP 3.0 Motherboard
SiS730Universal AGP Motherboard
SiS733Universal AGP Motherboard
SiS735Universal AGP Motherboard
SiS740no AGP slot
SiS741Universal 1.5V AGP 3.0 Motherboard
SiS745Universal AGP Motherboard
SiS746Universal 1.5V AGP 3.0 Motherboard
SiS748Universal 1.5V AGP 3.0 Motherboard
SiS755Universal 1.5V AGP 3.0 Motherboard
SiS756no AGP slot: PCI-Express
SiS760Universal 1.5V AGP 3.0 Motherboard
VIA CLE266no AGP slot
VIA CN400no AGP slot
VIA K8M800Universal 1.5V AGP 3.0 Motherboard
VIA K8T800 (VT8385)Universal 1.5V AGP 3.0 Motherboard
VIA K8T800 ProUniversal 1.5V AGP 3.0 Motherboard
VIA K8T890no AGP slot: PCI-Express
VIA KLE133 (VT8361)no AGP slot
VIA KM133 (VT8365)Universal AGP Motherboard
VIA KM266 (VT8375)Universal AGP Motherboard
VIA KM400 (VT8378)Universal 1.5V AGP 3.0 Motherboard
VIA KT133 (VT8363)Universal AGP Motherboard
VIA KT266 (VT8366)Universal AGP Motherboard
VIA KT333 (VT8367)Universal AGP Motherboard (but some implementations are AGP 1.5V Motherboard)
VIA KT400 (VT8377)Universal 1.5V AGP 3.0 Motherboard
VIA KT600Universal 1.5V AGP 3.0 Motherboard
VIA KT880Universal 1.5V AGP 3.0 Motherboard
VIA KX133 (VT8371)Universal AGP Motherboard
VIA MVP3 (VT82C598AT)AGP 3.3V Motherboard
VIA P4M266 (VT8751)Universal AGP Motherboard (but most implementations are AGP 1.5V Motherboard)
VIA P4X266 (VT8753)Universal AGP Motherboard
VIA P4X266A (VT8752)Universal AGP Motherboard
VIA P4X333 (VT8754)Universal 1.5V AGP 3.0 Motherboard
VIA P4X400 (VT8754)Universal 1.5V AGP 3.0 Motherboard
VIA P4X533Universal 1.5V AGP 3.0 Motherboard
VIA PLE133 (VT8601A)no AGP slot
VIA PLE133T (VT8602)no AGP slot
VIA PM133 (VT8605)Universal AGP Motherboard
VIA PM800Universal 1.5V AGP 3.0 Motherboard
VIA PM880Universal 1.5V AGP 3.0 Motherboard
VIA Pro (VT82C691)AGP 3.3V Motherboard
VIA Pro 133 (VT82C693A)AGP 3.3V Motherboard
VIA Pro 133A (VT82C694X)Universal AGP Motherboard
VIA Pro 266 (VT8633)Universal AGP Motherboard
VIA PT800Universal 1.5V AGP 3.0 Motherboard
VIA PT880Universal 1.5V AGP 3.0 Motherboard
VIA PT880 ProUniversal 1.5V AGP 3.0 Motherboard
VIA PT894no AGP slot: PCI-Express
VIA PT894 Prono AGP slot: PCI-Express

Final Words

Keep in mind that there are plenty of things which can go wrong when you plug an AGP card into an AGP motherboard. Just because they're supposed to be compatible doesn't mean that they're going to work. The information given above just tells you about their signaling voltage and speed compatibility. There are other problems which can prevent video cards and motherboards from working together that have nothing to do with the issues listed above.

Pseudo AGP Implementations

Page 31 - AGP 2.0 spec
The corelogic is required to support all signals required to:
1. Allow the A.G.P. master to enqueue requests and
2. Transfer data at 1x or 2x.
The corelogic may optionally support:
1. Data transfers at 4x or
2. Fast Write (FW) transactions to the A.G.P. master.
The A.G.P. master may optionally choose:
1. How it enqueues requests or
2. The rate at which it transfers data or
3. If it supports FW transactions.

Page 184 - AGP 2.0 spec
The A.G.P. interface can be classified by its signaling voltage level and maximum transfer rate capability.Interoperability of a particular add-in card with a particular motherboard is dependent only on the signaling levels.Signaling level is determined by the value of the Vddq I/O interface voltage. If the add-in card and the motherboardhave the same Vddq or if the motherboard has a universal connector, the add-in card will work with themotherboard. A key in the A.G.P. connector prevents add-in cards from being plugged into an incompatiblemotherboard. Universal connectors have no key and will accept either 1.5 or 3.3 volt Vddq add-in cards. TheTYPEDET# pin on the add-in card tells the universal motherboard which value of Vddq is to be supplied to theinterfaces as described above.A given part will also have a maximum transfer rate capability. However, every A.G.P. agent must be capable ofoperating at all lower transfer rates as well (i.e., a 4x mode part must also work at 2x and 1x rates). The transfer rateactually used is determined at configuration time and is likely to be the largest common rate between the A.G.P.master and target.

Page 42 - AGP 3.0 spec
AGPSTAT makes it look like you can have an AGP 3.0 8X only, AGP 3.0 4X only, orAGP 3.0 8X,4X

Troubleshooting Display Adapter Problems
PC Power Supplies Information
Useful Information
RollerCoaster Tycoon 3

Copyright © 2005 by Mark Allen

AGP (Accelerated Graphics port) is a modified version of PCI bus designed to speed up transfers to video cards.

Agp Universal Slot Machines

The Accelerated Graphics Port (also called Advanced Graphics Port) is a high-speed point-to-point channel for attaching a single device (generally a graphics card) to a computers motherboard, primarily to assist in the acceleration of 3D computer graphics. Many classify AGP as a type of computer bus, but this is something of a misnomer since buses generally allow multiple devices to be connected, while AGP does not. AGP originated from Intel, and it was first built into a chipset for the Pentium II microprocessor. AGP cards generally slightly exceed PCI cards in length and can be recognized by a typical hook at the inner end of the connector, which does not exist on PCI cards. Nowdays AGP is almost replaced by PCI-Express.

Agp Universal Slot Machine

AGP versions:

  • AGP 1.0: 3.3 volts signaling with speed multipliers 1x (267MB/s), 2x (533MB/s)
  • AGP 2.0: 1.5 volts signaling with speed multipliers 1x (267MB/s), 2x (533MB/s), 4x (1067MB/s)
  • AGP 3.0: 0.8 volts signaling with speed multipliers 4x (1067MB/s), 8x (2133MB/s)

In addition, in the world of workstations different AGP Pro cards exist with extra connectors which allow card to draw more power. In order to make life easier, the AGP standard defines some backward compatibilty. The AGP 1.0 specification requires that all implementations support the 1x speed multiplier at 3.3 volts. By default, when the AGP 1.0 machine powers up it selects the fastest speed multiplier supported by both the video card and the motherboard. If they both support 2x then they will run at 2x. Otherwise they run at 1x which is always implemented by all AGP 1.0 video cards and motherboards. The AGP 2.0 specification has a similar requirement. 2x and 1x support at 1.5 volts are required and 4x support is optional. The AGP 3.0 specification requires support for 8x. The 3.0 specification isn't as clear as the 1.0 and 2.0 specifications on the subject of requiring the lower multiplier but all AGP 3.0 almost all implementations support both 8x and 4x. As a result, you can completely ignore speed multipliers when you're checking for compatibility between an AGP video card and an AGP motherboard. If the video card and motherboard both support the same signaling voltage then there is always at least one common speed multiplier supported by both at that voltage. You only need to make sure that the video card and motherboard have at least one signaling voltage in common.

AGP cards and slots

Graphics Card TypesConnector Type*Description
AGP 3.3V Card3.3V slotSupports only 3.3V signaling. Available speeds 1x, 2x.
AGP 1.5V Card1.5V slotSupports only 1.5V signaling. Available speeds 1x, 2x, 4x.
Universal AGP CardDouble slottedSupports 3.3V and 1.5V signaling. Available speeds 1x, 2x at 3.3V and 1x, 2x, 4x at 1.5V.
AGP 3.0 Card1.5V slotSupports only 0.8V signaling. Available speeds 4x, 8x.
Universal 1.5V AGP 3.0 Card1.5V slotSupports 1.5V and 0.8V signaling. Available speeds 1x, 2x, 4x at 1.5V and 4x, 8x at 0.8V.
Universal AGP 3.0 CardDouble slottedSupports AGP 3.3v, 1.5V, and 0.8V signaling. Available speeds 1x, 2x at 3.3V and 1x, 2x, 4x at 1.5V and 4x, 8x at 0.8V.

Agp Universal Slots

*Different slots connectors have different position of key

The AGP connectors on the motherboard are keyed to prevent insertion of AGP cards which would be damaged if plugged in. An AGP 3.3V motherboard connector can only accept AGP cards which have the 3.3V slot. If you try to insert a card without a 3.3V slot into an AGP 3.3V motherboard connector, the card will bump into the connector key and cannot be inserted. Likewise an AGP 1.5V motherboard connector can only accept AGP cards with the 1.5V slot. An AGP universal motherboard connector has no keys and therefore can accept any kind of AGP card. An AGP card with both voltage slots can be plugged into any kind of AGP motherboard connector. If you can plug an AGP card into an AGP motherboard connector, then neither the card nor the motherboard will be damaged (assuming they obey the AGP specifications).

Slot

AGP pinout

3.3 Volt Boards

Universal Boards

1.5 Volt Boards

Pin #Side ASide BSide ASide BSide ASide B
1+12VOVRCNT#+12VOVRCNT#+12VOVRCNT#
2TYPEDET#+5.0VTYPEDET#+5.0VTYPEDET#+5.0V
3Reserved5.0VReserved5.0VReserved5.0V
4USB-USB+USB-USB+USB-USB+
5GroundGroundGroundGroundGroundGround
6INTA#INTB#INTA#INTB#INTA#INTB#
7RST#CLKRST#CLKRST#CLK
8GNT#REQ#GNT#REQ#GNT#REQ#
9VCC 3.3VCC 3.3VCC 3.3VCC 3.3VCC 3.3VCC 3.3
10ST1ST0ST1ST0ST1ST0
11ReservedST2ReservedST2ReservedST2
12PIPE#RBF#PIPE#RBF#PIPE#RBF#
13GroundGroundGroundGroundGroundGround
14ReservedReservedWBF#ReservedWBF#Reserved
15SBA1SBA0SBA1SBA0SBA1SBA0
16VCC 3.3VCC 3.3VCC 3.3VCC 3.3VCC 3.3VCC 3.3
17SBA3SBA2SBA3SBA2SBA3SBA2
18ReservedSB_STBSB_STB#SB_STBSB_STB#SB_STB
19GroundGroundGroundGroundGroundGround
20SBA5SBA4SBA5SBA4SBA5SBA4
21SBA7SBA6SBA7SBA6SBA7SBA6
22KeyKeyReservedReservedReservedReserved
23KeyKeyGROUNDGROUNDGROUNDGROUND
24KeyKeyReserved3.3VauxReserved3.3Vaux
25KeyKeyVcc 3.3Vcc 3.3Vcc 3.3Vcc 3.3
26AD30AD31AD30AD31AD30AD31
27AD28AD29AD28AD29AD28AD29
28VCC 3.3VCC 3.3VCC 3.3VCC 3.3VCC 3.3VCC 3.3
29AD26AD27AD26AD27AD26AD27
30AD24AD25AD24AD25AD24AD25
31GroundGroundGroundGroundGroundGround
32ReservedAD STB1AD STB1#AD STB1AD STB1#AD STB1
33C/BE3#AD23C/BE3#AD23C/BE3#AD23
34Vddq 3.3Vddq 3.3VddqVddqVddq 1.5Vddq 1.5
35AD22AD21AD22AD21AD22AD21
36AD20AD19AD20AD19AD20AD19
37GroundGroundGroundGroundGroundGround
38AD18AD17AD18AD17AD18AD17
39AD16C/BE2#AD16C/BE2#AD16C/BE2#
40Vddq 3.3Vddq 3.3VddqVddqVddq 1.5Vddq 1.5
41FRAME#IRDY#FRAME#IRDY#FRAME#IRDY#
42Reserved3.3VauxReserved3.3VauxKEYKEY
43GroundGroundGroundGroundKEYKEY
44ReservedReservedReservedReservedKEYKEY
45VCC 3.3VCC 3.3VCC 3.3VCC 3.3KEYKEY
46TRDY#DEVSEL#TRDY#DEVSEL#TRDY#DEVSEL#
47STOP#Vddq 3.3STOP#VddqSTOP#Vddq 1.5
48PME#PERR#PME#PERR#PME#PERR#
49GroundGroundGroundGroundGroundGround
50PARSERR#PARSERR#PARSERR#
51AD15C/BE1#AD15C/BE1#AD15C/BE1#
52Vddq 3.3Vddq 3.3VddqVddqVddq 1.5Vddq 1.5
53AD13AD14AD13AD14AD13AD14
54AD11AD12AD11AD12AD11AD12
55GroundGroundGroundGroundGroundGround
56AD9AD10AD9AD10AD9AD10
57C/BE0#AD8C/BE0#AD8C/BE0#AD8
58Vddq 3.3Vddq 3.3VddqVddqVddq 1.5Vddq 1.5
59ReservedAD STB0ReservedAD STB0#ReservedAD STB0#
60AD6AD7AD6AD7AD6AD7
61GroundGroundGroundGroundGroundGround
A62AD4AD5AD4AD5AD4AD5
63AD2AD3AD2AD3AD2AD3
64Vddq 3.3Vddq 3.3VddqVddqVddq 1.5Vddq 1.5
65AD0AD1AD0AD1AD0AD1
66ReservedReservedVrefgcVrefcgVrefgcVrefcg

The AGP bus is 32 bits wide, just the same as PCI is, but instead of running at half the system (memory) bus speed the way PCI does, it runs at full bus speed. This means that on a standard Pentium II motherboard AGP runs at 66 MHz instead of the PCI buss 33 MHz. This of course immediately doubles the bandwidth of the port; instead of the limit of 127.2 MB/s as with PCI, AGP in its lowest speed mode has a bandwidth of 254.3 MB/s. The AGP specification is in fact based on the PCI 2.1 specification, which includes a high-bandwidth 66 MHz speed.