Accelerated Graphics Port

Accelerated Graphics Port
1
Accelerated Graphics Port
AGP
Accelerated Graphics Port
Slot AGP 4x (AGP Universal Slot) (Orange, Top), PCI 2.2 Compliance (Blue, Bottom)
Year created
1996
Created by
Intel
Superseded by
PCI Express (2004)
Width in bits
32
Number of devices
1 device/slot
Speed
up to 2133 MB/s
Style
Parallel
The Accelerated Graphics Port (often shortened to AGP) is a high-speed point-to-point channel for attaching a
video card to a computer's motherboard, primarily to assist in the acceleration of 3D computer graphics. Originally it
was designed as a successor to PCI type connections. Since 2004, AGP has been progressively phased out in favor of
PCI Express (PCIe). By mid-2008, PCIe cards dominated the market and only a few AGP models were available.[1]
Advantages over PCI
As computers increasingly became graphically oriented, successive generations of graphics adapters began to push
the limits of PCI, a bus with shared bandwidth. This led to the development of AGP, a "bus" dedicated to graphics
adapters.
The primary advantage of AGP over PCI is that it provides a dedicated pathway between the slot and the processor
rather than sharing the PCI bus. In addition to a lack of contention for the bus, the direct connection allows for higher
clock speeds. AGP also uses sideband addressing, meaning that the address and data buses are separated so the entire
packet does not need to be read to get addressing information. This is done by adding eight extra 8-bit buses which
allow the graphics controller to issue new AGP requests and commands at the same time with other AGP data
flowing via the main 32 address/data (AD) lines. This results in improved overall AGP data throughput.
In addition, to load a texture, a PCI graphics card must copy it from the system's RAM into the card's Video
memory, whereas an AGP card is capable of reading textures directly from system RAM using the graphics address
remapping table, which reapportions main memory as needed for texture storage, allowing the graphics card to
access them directly.[2] The maximum amount of system memory available to AGP is defined as the AGP aperture.
Accelerated Graphics Port
2
History
The AGP slot first appeared on x86 compatible system boards based on
Socket 7 Intel P5 Pentium and Slot 1 P6 Pentium II processors. Intel
introduced AGP support with the i440LX Slot 1 chipset on August 26,
1997, and a flood of products followed from all the major system board
vendors.[3]
The first Socket 7 chipsets to support AGP were the VIA Apollo VP3,
SiS 5591/5592, and the ALI Aladdin V. Intel never released an
AGP-equipped Socket 7 chipset. 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.[4]
An AGP card
Early video chipsets featuring AGP support included the Rendition Vérité V2200, 3dfx Voodoo Banshee, Nvidia
RIVA 128, 3Dlabs PERMEDIA 2, Intel i740, ATI Rage series, Matrox Millennium II, and 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 MHz bus clock, with its
resulting doubled bandwidth over PCI, and bus exclusivity. Examples of such cards were the Voodoo Banshee,
Vérité V2200, Millennium II, and S3 ViRGE GX/2. 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.)
Microsoft first introduced AGP support into Windows 95 OEM Service Release 2 (OSR2 version 1111 or 950B) via
the USB SUPPLEMENT to OSR2 patch.[5] After applying the patch the Windows 95 system became Windows 95
version 4.00.950 B. The first Windows NT-based operating system to receive AGP support was Windows NT 4.0
with Service Pack 3, introduced in 1997. Linux support for AGP enhanced fast data transfers was first added in 1999
with the implementation of the AGPgart kernel module.
Versions
Intel released "AGP specification 1.0" in 1997.[6] It included both the 1× and 2× speeds. Specification 2.0
documented AGP 4×[7] and 3.0 documented 8×.[8] Available versions include:
AGP and PCI: 32-bit buses operating at 66 and 33 MHz respectively
Specification Speed Pumping Rate (MB/s) Frequency (MHz) Voltage (V)
PCI
-
single
133
33
3.3/5
AGP 1.0
1×
single
266
66
3.3
AGP 1.0
2×
double
533
66
3.3
AGP 2.0
4×
quad
1066
66
1.5
AGP 3.0
8×
octuple
2133
66
0.8
AGP 3.5 *
8×
octuple
2133
66
0.8
* 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 Compatibility section.
Accelerated Graphics Port
3
Official extensions
AGP Pro
It is an official extension for cards that required more electrical power.
It is 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.[9]
AGP graphics card (Apple Macintosh)
64-bit AGP
A 64-bit channel was once proposed as an optional standard for AGP
3.0 in draft documents,[10] 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.
AGP Pro graphics card
Internal AGP interface
Ultra-AGP, Ultra-AGPII
It is an internal AGP interface standard used by SiS for the north bridge controllers with integrated graphics.
The original version supports same bandwidth as AGP 8×, while Ultra-AGPII has maximum 3.2GB/s
bandwidth.
PCI-based AGP ports
AGP Express
Not a true AGP interface, but allows an AGP card to be connected over the legacy PCI bus on a PCI
Express motherboard. It is a technology used on motherboards made by 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 (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
Accelerated Graphics Port
4
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
MSI to offer limited backwards compatibility with AGP. It is, effectively, a modified PCIe slot allowing
for performance comparable to an AGP 4×/8× slot,[11] but does not support all AGP cards; the
manufacturer published a list of some cards and chipsets that work with the modified slot.[12]
Compatibility
AGP cards are backward and 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), Geforce 6 Series
(6200, 6600/6600 LE/6600 GT only) and the ATI
Radeon
9500/9700/9800(R350)
(but
not
9600/9800(R360)). Some Geforce 6200 and Geforce
6600 cards will function with AGP 1.0 (3.3v) slots.
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.
Compatibility, AGP Keys on card (top), on slot (bottom)
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.
There are some proprietary systems incompatible with standard AGP; for example, 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 architecture (e.g., PC, Apple) may not work with others
due to firmware issues.
Accelerated Graphics Port
5
Mark Allen of Playtools.com made the following comments regarding Practical AGP Compatibility for AGP 3.0 and
AGP 2.0:
"...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."
Power consumption
Actual power supplied by an AGP slot depends upon the card used. The maximum current drawn from the various
rails is given in the specifications for the various versions. For example, if maximum current is drawn from all
supplies and all voltages are at their specified upper limits, an AGP 3.0 slot can supply up to 48.25 watts; this figure
can be used to specify a power supply conservatively, but in practice a card is unlikely ever to draw more than 40 W
from the slot, with many using less. AGP Pro provides additional power up to 110 W. Many AGP cards had
additional power connectors to supply them with more power than the slot could provide.
AGP Power Provisioning
Slot Type
AGP
3.3 V 5 V 12 V 3.3 V Aux 1.5 V 3.3 V1 12 V1 Power Total
6A
2A 1A
.375 mA
-
-
48.25 W2
AGP Pro110
7.6 A
9.2 A
50 to 110 W
AGP Pro50
7.6 A 4.17 A
25 to 50 W
1
from the extended part of the AGP connector
2
the AGP Pro specs imply a maximum of 25 W
2A
Legacy use
By 2010 few new motherboards had AGP slots. No new motherboard chipsets were equipped with AGP support, but
motherboards continued to be produced with older chipsets with support for AGP.
Graphics processors of this period use PCI-Express, a general-purpose (not restricted to graphics) standard that
supports higher data transfer rates and full-duplex. To create AGP-compatible graphics cards, those chips require an
additional PCIe-to-AGP bridge-chip to convert PCIe signals to and from AGP signals. This incurs additional board
costs due to the need for the additional bridge chip and for a separate AGP-designed circuit board.
Various manufacturers of graphics cards continued to produce AGP cards for the shrinking AGP user-base. The first
bridged cards were the GeForce 6600 and ATI Radeon X800 XL boards, released during 2004-5.[13][14] In 2009
AGP cards from Nvidia had a ceiling of the GeForce 7 Series. In 2011 DirectX 10-capable AGP cards from AMD
vendors (Club 3D, HIS, Sapphire, Jaton, Visiontek, Diamond, etc.) included the Radeon HD 2400, 3450, 3650, 4350,
4650, and 4670. The HD 5000 AGP series mentioned in the catalyst software was never available. There were many
problems with the AMD Catalyst 11.2 - 11.6 AGP hotfix drivers under Windows 7 with the HD 4000 series AGP
video cards;[15] use of 10.12 or 11.1 AGP hotfix drivers is the recommendedWikipedia:Manual of Style/Words to
watch#Unsupported attributions workaround. Several of the vendors listed above make available past versions of the
AGP drivers.
Accelerated Graphics Port
References
[1]
[2]
[3]
[4]
[5]
AGP almost at the end, Softpedia (http:/ / news. softpedia. com/ news/ AGP-Almost-at-the-End-of-the-Road-87316. shtml)
What is AGP? (http:/ / www. sysopt. com/ features/ mboard/ article. php/ 3549951), SysOpt, September 19, 2003.
Intel 440LX AGPset (http:/ / www. intel. com/ design/ chipsets/ datashts/ 290564. htm), Intel, accessed October 18, 2007.
Lal Shimpi, Anand. Chipset Guide (Socket 7) (http:/ / www. anandtech. com/ showdoc. aspx?i=155& p=1), Anandtech, August 1, 1997.
Which version of Windows 95 supports AGP? (http:/ / www. computerhope. com/ issues/ ch000145. htm), ComputerHope, accessed October
18, 2007.
[6] Accelerated Graphics Port Interface Specification Rev. 1.0 (http:/ / www. playtool. com/ pages/ agpcompat/ agp10. pdf), Intel, accessed
October 18, 2007.
[7] AGP 4×: Faster Data Transfer & Better-Quality Images (http:/ / www. smartcomputing. com/ editorial/ article. asp?article=articles/ archive/
g0801/ 35x01/ 04g01. asp), Smart Computing, January 2000.
[8] AGP 3.0 Specification (http:/ / download. intel. com/ support/ motherboards/ desktop/ sb/ agp30. pdf), Intel, accessed October 9, 2011.
[9] AGP Pro 1.1a specification (http:/ / www. motherboards. org/ files/ techspecs/ apro_r11a. pdf)
[10] Draft AGP8× Interface Specification Rev. 0.91R (http:/ / web. archive. org/ web/ 20010613041316/ www. intel. com/ technology/ agp/
downloads/ agp8x_v091R_042401. pdf)
[11] MSI K8N Neo3-F Motherboard Review—What's an AGR video slot? (http:/ / www. pcstats. com/ articleview. cfm?articleid=1806&
page=2)
[12] List of cards and chipsets that work with the MSI AGR port (http:/ / web. archive. org/ web/ 20081116224856/ http:/ / www. msi. com. tw/
html/ products/ mainboard/ agr/ 7135agr. pdf)
[13] Gasior, Geoff. Nvidia's GeForce 6600 GT AGP graphics card: Bridging backwards (http:/ / techreport. com/ articles. x/ 7624), Tech Report,
November 16, 2004.
[14] Gasior, Geoff. ATI's new AGP Radeons: A bridge is born (http:/ / techreport. com/ articles. x/ 8344), Tech Report, May 20, 2005.
[15] AMD community forums (http:/ / forums. amd. com/ game/ messageview. cfm?catid=279& threadid=152471& highlight_key=y&
keyword1=agp)
This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November 2008 and
incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.
External links
• Archived AGP Implementors Forum (http://web.archive.org/web/20061010060709/http://www.agpforum.
org/)
• AGP specifications: 1.0 (http://www.playtool.com/pages/agpcompat/agp10.pdf), 2.0 (http://www.
motherboards.org/files/techspecs/agp20.pdf), 3.0 (http://members.datafast.net.au/dft0802/specs/agp30.
pdf), Pro 1.0 (http://web.archive.org/web/20021003222339/http://www.agpforum.org/downloads/
apro_r10.pdf), Pro 1.1a (http://web.archive.org/web/20021003222339/http://www.agpforum.org/
downloads/apro_r11a.pdf)
• AGP Compatibility For Sticklers (http://www.playtool.com/pages/agpcompat/newagp.html)
• AGP pinout (http://pinouts.ru/Slots/agp_pinout.shtml)
• AGP expansion slots (http://www.motherboards.org/articles/tech-planations/920_4.html)
• AGP compatibility (http://www.playtool.com/pages/agpcompat/agp.html) (with pictures)
• Ultra-AGPII Technology (http://www.sis.com/elibrary/elibrary_index00_000012.htm)
• PCI Specifications Documents (http://members.datafast.net.au/dft0802/specs.htm) contains AGP specs.
• Universal Accelerated Graphics Port (UAGP) (http://www.microsoft.com/whdc/archive/uagp.mspx)
• How Stuff Works - AGP (http://computer.howstuffworks.com/agp.htm)
• A discussion from 2003 of what AGP aperture is, how it works, and how much memory should be allocated to it.
(http://web.archive.org/web/20050804000048/http://www.ocfaq.com/article.php/overclocking/vidcard/
43)
6
Article Sources and Contributors
Article Sources and Contributors
Accelerated Graphics Port Source: http://en.wikipedia.org/w/index.php?oldid=598272499 Contributors: *drew, 64.104.217.xxx, ABF, AGtheKiLLER, Aaron Schulz, Abdul Muntaqim,
Acabashi, ActivExpression, Ae7flux, Aeons, Agoode, Alakasam, Aldie, Alecv, Aliquidparadigm, Alistair1978, Aluvus, Andrew sh, Andyjsmith, Angela, Angelic Wraith, Arndbergmann,
Arthena, Berkut, Bevo, Bgks, Bgwhite, Bmicomp, Bovineone, Brolin Empey, Btrujill, Calebddd, CanisRufus, Ceros, Changtaiyeh, Chmod007, ChrisGualtieri, ChrisJMoor, Chrislk02, Click23,
Conversion script, Crimsonfox, Crispmuncher, Crusadeonilliteracy, Crusader83, Cwolfsheep, Cybercobra, Damian Yerrick, DannyKitty, Delirium, DennisTT, Denniss, Denny, DerHexer,
Dkyeager, Don4of4, Doxent, Dragunov, Drahardja, Drisdelle461, E23, ESkog, Edward321, Ellmist, Endlessnameless, Engineerism, EpiVictor, Evan-Amos, Evanh, Evice, Falcon9x5, Fastily,
Fiftysixfifty, Firsfron, Fiskars007, Frap, Fredrik, Frozenport, Fsiler, Gdo01, GermanX, Giltramirez, Giraffedata, GoldDragon, Gracefool, Graham87, GrandDrake, GreetingsEarthling, Grundig,
HaZaRd, Hadal, Harvester, Hashar, Hellbus, Heron, Hopp, Hyins, Imroy, Intgr, Invader Phlegm, Jacob Poon, Jandalhandler, Java7837, Jcw69, Jeff G., Jeffthejiff, Jeremy Visser, Jeremypv,
JesseW, JigPu, Jodamn, Joe The Dragon, JoeShead, JonHarder, Jonverve, Jpgordon, JulesH, Julianprescott2604juuly, Karam.Anthony.K, Kb, Kelly Martin, Kevin, Kiand, Kinema, Kingpin13,
KnowBuddy, Krash, Kyng, L Kensington, Lmatt, Luna Santin, M7, Mandarax, Manifestation, Mark Grant, Masterjosh, MatthewWilcox, MaxEnt, Mdnavman, Merovingian, Mgedmin,
MisterSmiley, Miterdale, Mjb, Modster, Mortense, Mulad, Mysidia, Nikai, Nixdorf, Norm, Norm mit, Oji The Unseen, Oliverdl, Olki, Onecallednick, Onorem, Optim, OrgasGirl, Oshwah,
Pabouk, Pascal.Tesson, Patcat88, Paulka, Pavel Vozenilek, Pedant17, Pinar, Pit, Plugwash, Pmsyyz, Pol098, PranksterTurtle, Quoth the Raven, RBBrittain, Ramu50, Rchandra, Rdsmith4, Red
Vox, RegaLEaglE00, Reuben, Rhododendrites, Rich Farmbrough, Rigurat, Rilak, Roadahead, Rocastelo, Rogerdpack, SC07, SNEST2, Saxbryn, ShakingSpirit, Shandris, ShaunOfTheLive,
SickTwist, Snickerdo, Splash, Stephen Gilbert, Stonehead, Stuart P. Bentley, Superus.ijhgkjh, Swaaye, Synchrite, TRosenbaum, Tannin, Tarquin, Template namespace initialisation script,
TexasAndroid, The Thing That Should Not Be, The Wild Falcon, TheJosh, Thehb3d, Theodolite, Thue, Tigeron, Timharwoodx, Timl, Todd Vierling, Topbanana, Tothwolf, Triplight,
TubularWorld, Ukexpat, Unyoyega, VampWillow, Warpozio, Wasted Sapience, Wavelength, Wernher, Widefox, Wiki fanatic, Windkin, WojPob, Yamla, Yerpo, Yggdræsil, Yurik, Zac67,
ZeroOne, Zosma, Zyqqh, Zzuuzz, Zzzplayer, Милан Јелисавчић, 358 anonymous edits
Image Sources, Licenses and Contributors
file:Slots AGP & PCI on Motherboard P4VMM2 MCS.JPG Source: http://en.wikipedia.org/w/index.php?title=File:Slots_AGP_&_PCI_on_Motherboard_P4VMM2_MCS.JPG License:
Creative Commons Attribution-Sharealike 3.0 Contributors: User:Julianprescott2604juuly
Image:AGP-Video-Card.jpg Source: http://en.wikipedia.org/w/index.php?title=File:AGP-Video-Card.jpg License: Public Domain Contributors: Evan-Amos
File:NVIDIA GeForce4 Ti 4600 Mac.jpg Source: http://en.wikipedia.org/w/index.php?title=File:NVIDIA_GeForce4_Ti_4600_Mac.jpg License: Public Domain Contributors: Hyins
File:Quadro ELSA GLoria II Pro.jpg Source: http://en.wikipedia.org/w/index.php?title=File:Quadro_ELSA_GLoria_II_Pro.jpg License: Public Domain Contributors: Hyins
Image:AGP & AGP Pro Keying.svg Source: http://en.wikipedia.org/w/index.php?title=File:AGP_&_AGP_Pro_Keying.svg License: Creative Commons Attribution-Sharealike 2.5
Contributors: Original uploader was JigPu at en.wikipedia Later versions were uploaded by Aluvus at en.wikipedia.
License
Creative Commons Attribution-Share Alike 3.0
//creativecommons.org/licenses/by-sa/3.0/
7