The video card, also called the graphics card, is a component of a computer that handles all output that is displayed on a monitor. Video cards can either be onboard the system board, or as expansion cards attached to the system board. In the case of expansion cards, video cards can be placed into PCI, AGP, or PCI Express expansion slots. In any case, the video card will contain its own processor, called the GPU (graphics processing unit) that will perform all calculations to display graphics, hence freeing up processing time from the computer's CPU. Graphics cards also contain their own memory, called video memory, which is reserved entirely for the graphics card, which frees up system memory.

As mentioned above, video cards come in three slots: PCI, AGP, and PCIe. PCI slots are the oldest expansion slots currently used, and speed is split amongst all devices connected to such slots. AGP slots are built specifically for video cards, reserve all of the bandwidth for one single device, and offer a co-processor on the system board to help the video card along. These slots were the old favorite, but are quickly being phased out and replaced with the faster and cheaper PCI Express slot. PCI Express (or PCIe) is the latest advancement to graphics slots. While PCIe can be used to any type of card, it has found a place for video cards with its PCIe x16 size slot. These offer tremendous bandwidth to cards, and this bandwidth is not split among every PCIe slot.

Stands for …, SLI is a method used by graphic chip manufacturer NVIDIA to allow two video cards to run together in order to improve video quality. These cards are only available on select system boards that utilize PCIe and have two PCIe x16 slots. Any board that is capable of supporting SLI will usually say so. When using SLI, both video cards need to be identical and support SLI.

There are some very important things to understand when considering an SLI solution. While it will increase the framerate in games (frames per second), anything beyond 60 frames per second is indistinguishable to the human eye, and there will appear to be no difference. SLI is only useful when running games are very high resolutions on large monitors or plasma/LCD television sets, or when using a great number of monitors for a computer system. If neither of these cases is true, SLI is not necessary for a computer system. Another important consideration involving SLI is based around the fact that the video card consumes more power than any other component in a computer. The addition of a second video card will vastly increase power consumption and will incur long-term costs to maintain.

When purchasing video cards, the primary thing to consider is the speed of the GPU, the amount of video memory on the cards, and the interface type (slot type). The fastest cards with the most memory are most useful only if you plan to be playing a lot of the latest and greatest games with extensive 3d worlds and complicated models. Whenever you decide to purchase a video card, consider what tasks you will be using the computer for, and whether or not more power is necessary. The more powerful the video card, the more power it will consume, as the speed is directly proportional to the power consumed. Video cards are among the highest power consuming components in computer systems, and the long-term costs should be considered when purchasing a card.