Video Card Slots Defined

When it comes to the video card slot (also called a “bus”), a lot of acronyms are thrown around: PCI, AGP, PCIe. But what do they all mean? If you’re not a computer designer, there’s really no reason that you should know. Fortunately, all that’s really important for you most of the time is that you know which types of slots your computer has, so you know what you can video cards you can plug into them. However, most people are just a little curious about what it all means. For you, here is a breakdown of what these video card slots are all about.

PCI

It’s important to note that those slots in your computer are not necessarily just for graphics cards. The PCI stands for Peripheral Component Interconnect and it can be used for modems, network cards, sound cards, just about any peripheral hardware device you want to add to your computer. In fact, in modern computers, PCI slots are not even used for video. The bandwidth requirements for modern video have become so great that conventional PCI slots cannot support most modern video cards. However, you can still find PCI video cards if PCI slots are all you have.

AGP

AGP, or Advanced Graphics Port, was the next evolution in video card/video card bus technology. It was created in response to a need for greater bandwidth for quality graphics. The way it gets this is by providing a dedicated resource to the video card, as opposed to the PCI slot which would share bandwidth with other applications. Also, the AGP has additional data buses to keep data flowing. Also, the AGP is able to use the Graphics Address Remapping Table (GART) to read textures directly, rather than having to copy it onto the card’s framebuffer from the system’s RAM and then reading it from there, as PCI video cards had to do. You can only use an AGP card if your computer has an AGP slot. If not, you are stuck with PCI (in today’s computers you will be using PCI express, see below). In addition, your computer probably doesn’t have more than one AGP slot, so if you want to use two video cards, you will need to use something other than AGP for one.

PCI Express

PCI Express, or PCI-E or PCIe, is the current standard in video card bus technology. New computers will use PCIe slots exclusively for graphics cards, although you can still find and use PCI and AGP video cards for your computer if your computer supports them. They are based on a point-to-point serial concept rather than a parallel bus concept, which allows for more efficient data streaming. PCIe slots are defined as x1, x2, x4, x8, x16 and x32. These represent the number of lanes through which data can stream. You will most likely be looking for x16, which is the most common large size for the typical user.