AGP, as we already know, stands for Accelerated Graphics Port. And as the name implies, AGP is intended for use with the video subsystem of a computer. Intel defines AGP as a "high performance, component level interconnect targeted at 3D graphical display applications and is based on a set of performance extensions or enhancements to PCI."
So what does all of that mean? It means that, AGP, even though it can be used as a 2D graphics solution, is optimized for use as a 3D accelerator. AGP is much more than a mere "extension" of the PCI bus, many of you know that the PCI bus currently runs at a horrible 33MHz which is one of our most commonly experienced bottlenecks. AGP on the other hand has the capability of running at up to 4 times the PCI bus speed, (in this case 4 x 33 = 133MHz) which allows it to sustain noticeably higher data transfer rates than standard PCI video cards. In turn, real time 3D acceleration can now be made possible if manufacturers implement the AGP specification to the best of their ability.
We've already shown that AGP has a greater potential than PCI because of its higher clock rate, but there is much more to the equation that we are overlooking, including transfer rates and bandwidth. For example, a normally clocked PCI bus (33MHz) can achieve a maximum of 132MB/s, and although that number may seem large it is miniscule in comparison with the demanded transfer rates by some of our beloved 3D games =) AGP on the other hand, running in 2x mode (@ 66MHz) can achieve a peak transfer rate of 528MB/s! AGP can obtain this peak rate because it is constantly transferring data including on both the rising and falling edges of the, in this case, 66MHz clock. AGP accomplishes this as well as higher sustained transfer rates by sideband transfers and pipelining so it can constantly transfer data without having to wait for another part of the system to transfer it. We can expect AGP running in 4x mode to give us transfer rates much greater than that, most likely in excess of 800 MB/s!!!
Now that's all nice and dandy, but there are still a few more advantages of AGP...lets talk about textures first. Ever wonder why you can't run GLQuake on your Monster 3D in any resolutions higher than 640 x 480? Well, simply because the Monster 3D only has 2MB of graphics memory (from now on it will be referred to as local RAM) dedicated to textures (the other 2MB being dedicated to frame/z buffers which will be explained later on) and 2MB of local RAM dedicated to textures isn't enough to provide for the enormous textures found in GLQuake. Well, you might ask, why don't we use that 64MB of RAM sitting right next to my video card? Its not that easy, your system RAM, unlike your local RAM can't be accessed as quickly as would be necessary to insure that you don't experience any slow downs. AGP on the other hand, provides a fast path to the system RAM so you don't have to worry about how much local RAM you have and you don't really have to worry about the speed at which it will be accessed.
bron
http://www.anandtech.com/showdoc.html?i=105
als je even gegoogled had kon je het vinden
maar goed ik hoop dat je hier mee verder kunt. en dit
geld dus voor alle systemen
AGP is much more than a mere "extension" of the PCI bus, daarom wordt
het gewoon als pci bus aangeduid. (denk ik
)
Kun je ook bevestigen door aida32 te draaien.
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Voor 3% gewijzigd door
Verwijderd op 02-05-2004 15:33
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