Geoff
VIP Member
The video card (also known as Graphics Processing Unit, or "GPU") is responsible for generating the output signal that is sent to your monitor. This in turn lets you interact with your computer. The role and nature of the video card has changed greatly over the last few years. As a result, specifying a video card for a system can be either very confusing or rather simple. After reading this you should have a better idea on how they work and how to choose one thats right for you.
Advances in 3D software and hardware now come out very quickly. New hardware is constantly developed, and software is written to take advantage of it (and vice versa). Thus, the market at the present time is such that most video cards are distinguished based on their 3D performance only--almost all will do a good job with regular 2D (Windows, non-gaming) tasks.
How do I know what card is right for me?: If you plan to play games or do 3D work, such as video editing or CAD, you will need to buy a video card, using integrated video simply wont do. You may be wondering, "what make should I get?" There are currently 2 main video card manufacturers, ATI and nVidia, although Volari is starting to pick up pace. Both ATI and nVidia make excellent GPU's, from a number of polls and peoples personal opinion, ATI is generally better for 3D work, such as video editing or CAD, and nVidia is best for gamers. But keep in mind that this is what most people have said, and doesn't mean that ATI is only good for work, and vice versa.
What is SLI, and what does it do?: SLI (also known as Scalable Link Interface) technology links two graphics cards together to provide scalability and increased performance. nVidia is the only company that has SLI, ATI uses crossfire. nVidia SLI takes advantage of the increased bandwidth of the PCI Express bus architecture, and features hardware and software innovations within nVidia GPUs' and nVidia MCP's (media and communications processors). Depending on the application, nVidia SLI can deliver as much as two times the performance of a single GPU configuration.
Role and Subsystems: The video card is a key component in the video subsystem, interacting with the system monitor. I also consider it a part of the system processing core, because for 3D work it does a lot of processing and must interact closely with the CPU, chipset and memory. Of course, this depends on how important video is to your PC use.
Related Components: The monitor, motherboard and CPU are all closely related to the video card. The monitor's relationship is fairly obvious, and the capabilities of the two components must be matched in a specific way (see below). The video card must also be selected to match the appropriate bus slot on the motherboard, there are currently 3 different slots for a video card; PCI, AGP 2x/4x/8x, and PCI-Express 16x. PCI-Express is the newest as of now, and PCI is the oldest card that is still in use.
Integrated Or Dedicated: You must first decide if you are going to get a dedicated video card, or video integrated onto the motherboard. This decision usually comes down to cost and your video needs. If you go with integrated video, this becomes part of the motherboard selection decision.
System Bus Interface: The video card plugs into a system bus slot intended for it. On most newer systems PCI-E has become the standard for video cards, but AGP video cards are still fairly common, type of video cards. There are different speeds of AGP cards and slots. Although there are also very old video cards that use the now defunct VLB and ISA system buses.
Video Chipset: The heart of the video is its internal processor, which is called the video chipset. The chipset is the key determinant of the attributes of the video card as a whole, especially its 2D and 3D graphic acceleration capabilities. The other components determine the specific implementation of the particular card you are looking at, but the video chipset determines the "family" that the card falls into and many of its characteristics in terms of performance and software support.
Supported Resolutions and Color Depths: Video cards support a number of different output resolutions; the most common are800x600, 1024x768, 1280x1024 and 1600x1200. The higher the resolution, the more information that is displayed on the screen, and the more power and memory is required of the video card. Similarly, support for more colors for each pixel requires more speed and memory storage.
Processing Speed: Some video cards are available in multiple versions, using the same chipset but varying in terms of the speed that the video chip runs. Faster chips produce better performance for 3D applications.
Video Memory Size: Video cards have their own high-speed memories that are used for two purposes. The first is to hold the color and brightness information for each pixel (dot) on the screen: larger resolutions and higher color depths require more memory to store the additional information. The second is for use by the video processor to speed up and buffer graphical calculations, especially for 3D operation. The average memory that is used on current video cards are either 128MB or 256MB, although they do have some 512MB cards; all of the memory above 8 MB is used for calculations and buffers in software designed to take advantage of it.
Video Memory Technology: To improve performance, video cards often use faster memory technologies than the regular system memory used by the PC as a whole. Faster technologies such as GDDR3 enable higher performance.
Quality Selection Criteria: The quality of a video card can be considered in two ways: the quality of the physical components, and the quality of the output produced as well. (The output quality is closely related to several of the performance issues above):
Construction: Since the chipset is the core of the video card, it is commonly used by many different manufacturers to make different specific video card types. Better ones of these are better constructed and have better support components than cheap ones.
Refresh Rates: A conventional monitor display is produced by scanning an electron beam very quickly across the entire surface of the screen. The phosphorescent display then immediately begins to fade and must be refreshed, many times per second. The number of times per second that the screen is redrawn is called its refresh rate. Refresh rates are important because if they are too low, flickering becomes noticeable and this causes eye strain; the usual number considered as a minimum for acceptable quality is 72 Hz. Higher resolutions make it more difficult to keep refresh rates high, as do higher color depths. So to get 72 Hz on a 640x480 resolution output is trivially simple for today's cards; getting 72 Hz on a 1600x1200 output much more difficult because you are dealing with six times as much information. 85 Hz or higher is even better than 72 Hz. High refresh rates require sufficient speed from the video card's video memory and RAMDAC, the component that produces the output signal from the video memory. It also requires that the monitor be able to support the refresh rate being used by the video card for the given resolution. See the discussion of monitors for more.
Video Driver Quality And Support: Video card performance and stability is as much a function of the operating system drivers that interface with the hardware as it is a function of the hardware itself. Some companies have a much better reputation than others for writing high-quality, bug-free drivers, and also for keeping them updated. Bad or out-of-date drivers can cause a host of system problems, and poor manufacturer support may make it impossible for you to upgrade your operating system in the future.
BIOS Upgradeability: The video card has its own video BIOS, and like the system BIOS on the motherboard this can be updated to improve performance or correct problems. The comments above about video drivers also apply here.
Advances in 3D software and hardware now come out very quickly. New hardware is constantly developed, and software is written to take advantage of it (and vice versa). Thus, the market at the present time is such that most video cards are distinguished based on their 3D performance only--almost all will do a good job with regular 2D (Windows, non-gaming) tasks.
How do I know what card is right for me?: If you plan to play games or do 3D work, such as video editing or CAD, you will need to buy a video card, using integrated video simply wont do. You may be wondering, "what make should I get?" There are currently 2 main video card manufacturers, ATI and nVidia, although Volari is starting to pick up pace. Both ATI and nVidia make excellent GPU's, from a number of polls and peoples personal opinion, ATI is generally better for 3D work, such as video editing or CAD, and nVidia is best for gamers. But keep in mind that this is what most people have said, and doesn't mean that ATI is only good for work, and vice versa.
What is SLI, and what does it do?: SLI (also known as Scalable Link Interface) technology links two graphics cards together to provide scalability and increased performance. nVidia is the only company that has SLI, ATI uses crossfire. nVidia SLI takes advantage of the increased bandwidth of the PCI Express bus architecture, and features hardware and software innovations within nVidia GPUs' and nVidia MCP's (media and communications processors). Depending on the application, nVidia SLI can deliver as much as two times the performance of a single GPU configuration.
Role and Subsystems: The video card is a key component in the video subsystem, interacting with the system monitor. I also consider it a part of the system processing core, because for 3D work it does a lot of processing and must interact closely with the CPU, chipset and memory. Of course, this depends on how important video is to your PC use.
Related Components: The monitor, motherboard and CPU are all closely related to the video card. The monitor's relationship is fairly obvious, and the capabilities of the two components must be matched in a specific way (see below). The video card must also be selected to match the appropriate bus slot on the motherboard, there are currently 3 different slots for a video card; PCI, AGP 2x/4x/8x, and PCI-Express 16x. PCI-Express is the newest as of now, and PCI is the oldest card that is still in use.
Integrated Or Dedicated: You must first decide if you are going to get a dedicated video card, or video integrated onto the motherboard. This decision usually comes down to cost and your video needs. If you go with integrated video, this becomes part of the motherboard selection decision.
System Bus Interface: The video card plugs into a system bus slot intended for it. On most newer systems PCI-E has become the standard for video cards, but AGP video cards are still fairly common, type of video cards. There are different speeds of AGP cards and slots. Although there are also very old video cards that use the now defunct VLB and ISA system buses.
Video Chipset: The heart of the video is its internal processor, which is called the video chipset. The chipset is the key determinant of the attributes of the video card as a whole, especially its 2D and 3D graphic acceleration capabilities. The other components determine the specific implementation of the particular card you are looking at, but the video chipset determines the "family" that the card falls into and many of its characteristics in terms of performance and software support.
Supported Resolutions and Color Depths: Video cards support a number of different output resolutions; the most common are800x600, 1024x768, 1280x1024 and 1600x1200. The higher the resolution, the more information that is displayed on the screen, and the more power and memory is required of the video card. Similarly, support for more colors for each pixel requires more speed and memory storage.
Processing Speed: Some video cards are available in multiple versions, using the same chipset but varying in terms of the speed that the video chip runs. Faster chips produce better performance for 3D applications.
Video Memory Size: Video cards have their own high-speed memories that are used for two purposes. The first is to hold the color and brightness information for each pixel (dot) on the screen: larger resolutions and higher color depths require more memory to store the additional information. The second is for use by the video processor to speed up and buffer graphical calculations, especially for 3D operation. The average memory that is used on current video cards are either 128MB or 256MB, although they do have some 512MB cards; all of the memory above 8 MB is used for calculations and buffers in software designed to take advantage of it.
Video Memory Technology: To improve performance, video cards often use faster memory technologies than the regular system memory used by the PC as a whole. Faster technologies such as GDDR3 enable higher performance.
Quality Selection Criteria: The quality of a video card can be considered in two ways: the quality of the physical components, and the quality of the output produced as well. (The output quality is closely related to several of the performance issues above):
Construction: Since the chipset is the core of the video card, it is commonly used by many different manufacturers to make different specific video card types. Better ones of these are better constructed and have better support components than cheap ones.
Refresh Rates: A conventional monitor display is produced by scanning an electron beam very quickly across the entire surface of the screen. The phosphorescent display then immediately begins to fade and must be refreshed, many times per second. The number of times per second that the screen is redrawn is called its refresh rate. Refresh rates are important because if they are too low, flickering becomes noticeable and this causes eye strain; the usual number considered as a minimum for acceptable quality is 72 Hz. Higher resolutions make it more difficult to keep refresh rates high, as do higher color depths. So to get 72 Hz on a 640x480 resolution output is trivially simple for today's cards; getting 72 Hz on a 1600x1200 output much more difficult because you are dealing with six times as much information. 85 Hz or higher is even better than 72 Hz. High refresh rates require sufficient speed from the video card's video memory and RAMDAC, the component that produces the output signal from the video memory. It also requires that the monitor be able to support the refresh rate being used by the video card for the given resolution. See the discussion of monitors for more.
Video Driver Quality And Support: Video card performance and stability is as much a function of the operating system drivers that interface with the hardware as it is a function of the hardware itself. Some companies have a much better reputation than others for writing high-quality, bug-free drivers, and also for keeping them updated. Bad or out-of-date drivers can cause a host of system problems, and poor manufacturer support may make it impossible for you to upgrade your operating system in the future.
BIOS Upgradeability: The video card has its own video BIOS, and like the system BIOS on the motherboard this can be updated to improve performance or correct problems. The comments above about video drivers also apply here.
BUt yeah, a good start for now 
