What is it?
A graphics card translates raw data inside your computer into a video signal that it sends to your computer monitor. In theory, the computer's main processor could do that job by itself, but it would place too much of a burden on it. Because it takes a huge amount of computer data to make up even a simple two-dimensional image on your screen, your computer's processor could not process other data, such as a word processing application. A graphics card solves that problem by using its own specialized processor, which is designed specifically to handle graphics data, so that the burden is taken off the main CPU. The better the graphics card, the more data it can process into images on your computer screen, and more data means richer colors, sharper details, and more elaborate 3D images. 

A graphics card looks like a small circuit board with a processor chip and several memory chips on the surface and a metal plate along one edge. The card fits into an expansion slot inside your computer, and the metal plate contains at least one port or socket that attaches to the cable on your monitor. 

Why would I want one?
If you want to play the latest 3D computer games, run 3D graphics design programs, or view DVD movies on your computer, then your graphics card is an essential component. To get the most out of the latest games or graphics applications, you should consider upgrading your graphics card on a regular cycle of two years or less. 

Around five years ago, people upgraded their graphics cards to achieve better 2D quality and "Windows acceleration". Nowadays, the 2D playing field is fairly level, and graphics cards are most often replaced in order to enjoy faster 3D graphics or motion video acceleration. You won't need such an upgrade for basic computer uses such as Internet browsing or word processing, but to enjoy the newest entertainment software, a graphics card upgrade is a necessity. 

How do I install and use it?
Before beginning the installation of a new graphics card, be sure to read the owner's manual thoroughly. Remove the card from the box and inventory all included parts to be sure that they are there. Remove any tape or other packaging that might be used for shipping protection. Before handling the card, touch a grounded piece of metal to discharge static electricity from your hands. 

Turn off your computer and unplug it from its power source. Detach the monitor cable from the computer. Open the computer case to access the internal components; this may require unscrewing several screws that hold the cover in place. Identify the correct expansion slot -- either a PCI slot or an AGP slot -- and if there is a graphics card already installed, remove it. Some computers, instead of using a removable graphics card, have the graphics components integrated directly onto the motherboard. In that case, it may be possible to configure a jumper or "dip switch" to tell the computer that you want to override the integrated graphics chip and use a graphics expansion card instead. Consult your computer or motherboard manual to see if this is the case, or whether the computer is only capable of using its own integrated graphics chip.

Once the existing graphics card or chip has been removed or disabled, insert the new graphics card into the expansion slot gently. Do not force the card into place; if it seems resistant, try rocking it gently into the slot one corner at a time. Screw the card's I/O shield into place, and replace the cover to your computer case. Attach the monitor cable to the monitor port on the graphics card, usually a serial port. Plug in your computer (and your monitor, if it is unplugged), and then turn on the computer and the monitor. 

If there is a problem with the new card, you may hear a series of beeps and the computer will refuse to boot. If so, turn it off, open the case and check to make sure the card is inserted correctly and completely into the expansion slot. If the card is installed correctly but the problem persists, you may need to reinstall the original graphics card for the time being, and get assistance from the card's manufacturer or from a trained technician. 

If there is no problem and the system starts normally, then get the installation or driver disk ready that came with the card, and wait for the operating system to finish loading. Insert the disk into the proper drive (usually the CD-ROM drive). If you're using Windows 95 or Windows 98, the computer should automatically read the disk in the drive. If it does not, click on the Start button, select Run, and then Browse. Locate a file called either Install or Setup to install the drivers (consult the documentation that came with the card). Follow the on-screen instructions. Normally, after the new drivers are installed, Windows will ask you to shut down the system and restart it, so that the new drivers can be loaded into memory. 

How do I go about buying one?
It isn't easy to categorize graphics cards into separate groups that are easily distinguished from one another. With some exceptions, however, the most expensive cards are geared towards power gamers and offer the highest level of 3D acceleration as their main feature. Other cards that are priced for the "budget PC" market often try for a more broad entertainment appeal, providing moderate 3D acceleration as well as DVD and MPEG video decoding, and the occasional extra feature such as TV output. There's usually a graphics card for every price level and performance level. 

When shopping for a new graphics card, there are several key specifications that you need to know, including bus type, memory size, fill rate, geometry processing, and video decoding. 

Bus Type: In computer terminology, a "bus" is simply a path for data to travel between two or more devices. The PCI bus, for example, connects the PCI expansion card slots to the memory and the chipset on the motherboard. Data can travel at a fast rate along the PCI bus, up to 132MB per second. For a long time, this fast data rate meant that most graphics cards used PCI expansion slots. But today there's an even faster data bus that is designed specifically for graphics cards: the AGP bus. 

AGP comes in three different flavors: AGP 1X, AGP 2X, and AGP 4X. At 1X, the AGP bus is twice as fast as PCI, with a transfer rate of 264MB/sec. At 2X, AGP is four times as fast as PCI, and with AGP 4X, you get data rates up to a whopping 1056MB/sec -- eight times faster than PCI. 

This does NOT mean that an AGP 4X graphics card actually runs eight times faster than a PCI card; it only means that when the card needs to access main memory, it can do so much more quickly. The performance difference between an AGP card and a PCI card in reality is not that great. Still, it's not surprising that most graphics cards today are made for AGP expansion slots, and if your computer has an AGP slot, we definitely recommend choosing an AGP graphics card. Refer to your computer's documentation to see which AGP level (1X, 2X or 4X) is supported and buy a card that is compatible with that AGP specification. If your computer does not have an AGP expansion slot, there's no need to worry since plenty of quality graphics cards for PCI expansion slots. If your computer is an older model with neither AGP slots nor PCI slots, it will not support today's graphics cards. 

Memory Size: All the images and textures that you see in a 3D computer game have to be stored in memory when the game is played, and they are pulled out of memory and used whenever the graphics card needs to draw them on the screen. A card with more memory can store textures that are larger and more detailed, and it can store more of them. It can also reach higher resolutions in both 2D and 3D and display a sharper image with more colors. Today, 32MB is becoming the standard for most graphics cards, and there are some cards that offer even more. 

Fill Rate: This is a measure of how many 3D pixels a graphics card can draw on the screen every second. It's usually measured in Megapixels (Mpixels -- one million pixels), but you will also see the term "Megatexels" (Mtexels) used. The difference is that for every pixel, there can be several textures; a texel is simply a texture applied to a pixel. Multiple textures are used to create 3D effects such as reflective surfaces, transparent objects, and so forth. To perform well, a graphics card needs to have a high fill rate in both Mpixels AND Mtexels. Not all manufacturers reveal the fill rates of their graphics cards, and in fact it is not a completely reliable measure of performance. But in general, you will want to find a card with a very high fill rate in order to enjoy the smoothest acceleration for 3D games. 

Geometry Processing: The creation of a 3D scene happens in two main steps or phases. First, the geometrical shapes that make up the 3D scene and the lighting of the scene are calculated (this is called the "transform & lighting" phase, or "T&L" phase), and then textures are applied to those bare shapes to make them appear like real objects (the "rendering" phase). In the past, your CPU did all the work in the T&L phase, and your graphics card did the work in the rendering phase. Today, however, there are graphics cards that have on-board geometry processors that process the T&L calculations in place of your CPU. This allows the 3D scene to be made up of many more polygons, so that objects appear less "blocky." It also frees up your CPU to work on other things like artificial intelligence for enemies in the game. Newer 3D games are designed for cards with on-board geometry processing. So, if gaming is your intention, a card with geometry processing is a good investment provided it fits within your budget. 

Video Decoding: If you have a DVD-ROM drive in your computer, you may want to play DVD movies on your computer screen. To do that, however, your computer needs to be able to decode the video data on the DVD disc, and that can be done either with a software program or a special hardware-decoding chip. Acceleration through a hardware decoder is usually much better and smoother than software decoding. Many graphics cards offer DVD video acceleration, but not all of them do the decoding in hardware. To find the best quality in DVD movie playback, check the description of a graphics card to see if it states whether the DVD acceleration is hardware-based or software-based. Sometimes you'll see the term "hardware-assisted", which is not true hardware acceleration. However, if your computer also has a fast CPU, then even software DVD decoding can produce results that are perfectly satisfactory. 

Other Features: Some graphics cards offer a TV-out port, which allows you to hook up a television set instead of a normal computer monitor. This can be good for watching DVD videos or playing 3D games on a larger screen. Some cards also offer video capture and editing features, which allow you to create video segments from home movies or other sources, among other things. Read about all the extra features that a graphics card offers, and see whether any of them make the card a more attractive choice for you.