AGP versus PCI-e

If you are just now in the process of upgrading from AGP to PCI-e, you are probably pretty far behind the game. But if you are wondering why you simply can't find any good video cards in AGP any longer, then you aren't the only one asking this question, I can assure you! Generally speaking, there is one simple reason why people have made the switch to PCI-e. That is that there are more capabilities and benefits of PCI-e than there are in AGP.

The first noticeable difference is the bandwidth. The PCI link is a 5GB/s connection. 80% of that (4GB/s) is actually being used to transmit information. This is why it is known as an 8-bit/10-bit encoding connection. You should also be aware that this information is bi-directional. Meaning that while 1 bit of data is incoming, the 1 bit of data can also be outgoing at the same time.

Unfortunately for AGP users, this type of connection doesn't have that same functionality. The truth is that an AGP connection can only send 2.1 GB/s of data. There are different modes which may be able to allow it to get slightly faster and maybe even up to 4GB/s. But regardless of which mode you are using, it is never as fast as the x16 PCI-e connection.

The second problem with AGP is that there is an issue with power. You can see many of the latest AGP cards on the market to see that they came with extra four pin connections. You can look at the Geforce 7800GS or the ATI Radeon X850XTPE which both have one, or you can see that the GeForce 6800 Ultra has two. Things aren't similar from the days that these cards were the hottest in the market. When you look at the AGP connection there is limited power, only reaching a maximum of 41.8 watts.

Sure, there was some additional life put into the AGP genre by adding those four pin connections. However, the PCI Express can give 75 watts through a single x16 connection and then another 75 watts with a six pin connection. There is definitely far more power able to get to the video card, increasing its capabilities.

In short, the AGP connection had problems in giving the video card the juice it needed to run at a speed necessary to run some of the latest applications and games. It was limited. The PCI Express technology will certainly be here to stay. Manufacturers have already made the move and even as of 2008 we were seeing that only 5% of those who were buying cards were purchasing AGP cards still. Now, late 2009, I would imagine anyone who is upgrading is making the jump to PCI-e.

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-By Dominic

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