My research is about the differences between the video card busses AGP and PCI express. When I put my first computer together the AGP bus was the new hot thing that was suppose to be so much better then the PCI slot they had been using previously. Now I have noticed that they have come out with a PCI express card that is suppose to be better then the AGP card. This got me to wonder why they went from AGP back to a type of PCI slot. The following is the research I did and what I have found out. It is also the reason that I want to build a new computer with a PCI Express card in it for my games.
Annotated Journal Articles
Wikipedia, the free encyclopedia: Accelerated Graphics Port, http://en.wikipedia.org/wiki/Accelerated_Graphics_Port
This is your basic encyclopedia information about the Accelerated Graphics Port or AGP for short. It tells about the advantages that the AGP has over the original PCI graphics cards. It then goes on to tell about the history of the the AGP Slot and cards from who created it and why. Next it goes into the different versions of the AGP slots and cards. Also it covers variations and compatibility of the cards. Finally it tells about the Use of the cards today. AGP uses a parallel connection and has speeds up to 2133 MB/s.
Wikipedia, the free encyclopedia: PCI Express, http://en.wikipedia.org/wiki/PCI_Express
This is your basic encyclopedia information about the PCI Express port and cards. It tells about the advantages that the PCI Express card has over the AGP interfaces and graphics cards. It gives an overview of the slot and how it interfaces with the main board and why it uses a serial connection as opposed to a parallel connection. It goes on to give a Hardware protocol summary that goes into the physical layer, the data link layer and the transaction layer. The hardware protocol talks about what slots different PCI cards can go in like a PCI card that has an x1 link can go in anything bigger. It also talks about how in the signal there clocking information is embedded. Under the transaction layer it talks about how they come up with how much information can be passed to and from the card at any time. It is said that the first generation card that has 16 lanes would be theoretically capable of 4 GB/s in each direction. It goes on to say that PCIe 2.0 doubles the bus standard's bandwidth from 2.5 Gbit/s to 5Gbit/s, meaning a x32 connector can transfer data at up to 16GB/s in each direction.
Cassio Lima: AGP Bus Tutorial, http://www.hardwaresecrets.com/article/155/1
This article starts off by talking about the original 32-bit PCI bus and its transfer rate of 133MB/s which really was not the transfer rate of just the video card since other things were connected to the bus and used some of the bandwidth. This rate was said to be insufficient for 3D applications and so AGP was created to solve this problem. It also says that AGP is not really a buss but more of a high performance point-to-point connection since the video card is the only thing connected to it. It goes on to tell about the 4 modes of AGP cards and the transfer rate of each of them. The x8 AGP had a transfer rate of 2,133 MB/s which is 16 times faster then that of the PCI bus. The last thing it shows in this article is the slots for the various AGP cards and a couple of the AGP cards. This would be a good article to read if you wanted to try and figure if you computer had an AGP slot or not.
Cassio Lima: PCI Express Bus Tutorial, http://www.hardwaresecrets.com/article/190/1
This article start out much like the other one talking about the PCI bus and then it moves in to talking about AGP. It says that AGP was starting to not be able to keep up with faster graphics chips and new network technologies and so PC Express was introduced to take care of that. Like the AGP slot PCI express is not really considered a bus the article states. It goes on to talk about the change from parallel communication to serial communication. While parallel communications is faster it suffers from some problems that prevent it from reaching higher clocks, because the higher the clock the greater the problems with magnetic interference and propagation delay. The article finishes off with a look at the different kinds of PCI express slots and a look at a PCI, an AGP, and a PCI Express card (pictured at bottom of screen). This would be a great place to look if you wanted to know if you had a PCI Express slot in your computer.
J. Kohrs: Tech Tip 17-Expansion Cards Part 3: PCI Express, http://www.geeks.com/techtips/2005/techtips-031005.htm
This is a great article that talks about the PCI Express card. The PCI Express card has a combination of two-way serial connections. Each one is called a lane or a link and they can transmit and receive data independently. There is no sharing of bandwidth since each lane is dedicated between two points. This article also talks about how PCI Express will be able to be used for more then just video cards. One advantage of having more then one PCI Express slot on a main board is the fact that more then one video card can be installed. By doing this you can have a video card for each display in a dual display scenario or you can use the resources of two cards for one display. This article has some great links to other websites when it talks about certain video cards and devices.
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