A graphics controller (also known as a video card or a graphics adapter) transfers the signal supplied by a computer's CPU to a video display unit called a monitor. A graphics controller takes over much of the control of the video signal from the CPU, so it carries its own special-purpose processor and memory. A faster graphics processor with more memory can send the monitor an image with more detail and more colors, and it can refresh the signal more often. If your monitor has a DVI (digital video interface) input connector, look for a controller card that provides a digital signal.
Every computer needs at least one graphics controller, but it's easy to choose a card that offers far more speed and performance than you really need. For the usual word processing, number crunching, and Web browsing, an inexpensive graphics controller often provides an entirely satisfactory image. Game players and graphic designers notice improvement with a more expensive card.
Chapter 10 contains a detailed description of a graphics controller's features and functions.
Unlike many other features and functions of a new computer that are built into the motherboard, the graphics controller is often a separate expansion card. It's easy for a manufacturer or a screwdriver shop to substitute a different card for the one they include in their standard configuration. Don't expect to make this kind of swap if you buy your computer at a chain store, where the computers on the shelf are preassembled and ready for you to take home without any alterations.
If you're shopping for a computer in a retail store that offers computers with a choice of graphics controllers, ask to see the same image on identical monitors. If you can't see any difference on the type of programs you expect to use, buy the computer with the less expensive card. Don't buy a more powerful card just because it looks great on video games that are designed to take advantage of all that enhanced performance unless you expect to play some of those games.
A more expensive and more powerful computer often includes a more powerful graphics controller, but you might save a bit of money by choosing a different card. Or if you or your children will use the computer for graphics-intensive games, consider replacing the standard controller with one that has more memory and faster performance.
As a rule of thumb, an inexpensive graphics controller with 32MB or 64MB of on-board memory should be adequate for most Windows XP users. For Windows Vista, look for a card with at least 128MB and a DirectX 9 class graphics processor. For full 3-D video on games and interactive television, try a card with as much memory and as much speed as you can afford.
In some computers, the fan mounted on the graphics controller card is the loudest thing inside the case, but you might not notice it in a noisy store. A card that provides the same performance with a big heat sink instead of a fan mounted over the graphics processor chip reduces the overall amount of noise that you computer produces.
High-performance graphics processor chips for game players often produce a lot of heat; the cards without fans are usually limited to the ones with slower and less powerful processors.
The refresh rate is the number of times per second that the video controller wipes and replaces the image on the monitor screen. Faster is better for monitors that use CRT displays, up to about 75 or 80 Hz or more. For most LCD displays, the refresh rate is 60 Hz, so the higher rates don't matter.
The image you see on a computer's monitor screen is a composite of many tiny dots called picture elements, or pixels. Resolution is the number of pixels that it takes to fill the monitor screen. The device driver software (the software that converts image information from the CPU to specific instructions for the graphics controller) supplied with your graphics controller can increase or decrease the resolution of the image that appears on the screen. The device driver also sets the maximum number of colors (each a slightly different shade) that the monitor can display. An image with more colors looks better because the different shades provide better definition.
The graphics controller must work harder to refresh an image with more colors or greater resolution, so a controller with more memory and a faster processor can produce a higher-quality image than one with fewer resources. In practice, this means that a card with more memory can accept a higher maximum resolution, refresh rate, and number of colors. In other words, look for a controller with more memory (up to 64 or 128MB) to produce a better-looking image. Cards with even more memory produce better results on games and other three-dimensional images, but they're not necessary for most other purposes.