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[ The PC Guide | The PC Buyer's Guide | Designing and Specifying PC Systems and Components | Designing PCs: Structure and Subsystems | PC Subsystem Design ]

Video Subsystem

The video subsystem is responsible for providing output display to the user, showing the results of the calculations and programs that the computer is running. It includes the following components:

  • Video cards (also part of the system processing core). Some systems also include other video-related components such as TV tuner cards, though I would normally consider these add-in optional peripherals.
  • Monitors.

The definition above is technically correct, and has been since the earliest PCs, but doesn't really convey the true essence of how important the video subsystem is in a modern PC. The earliest PCs used flickery monochrome text to "show the results of calculations", and that's all the video really had to do. Today, we use our computers for so much more than just calculations. Yet most of the communication from the PC to the user is still visual, through the video card and monitor. In fact, many PCs use nothing else.

Three very different aspects of the capabilities of the video subsystem, all of which influence the selection of both the video card and monitor, are these:

  • Performance: The ability of the PC to calculate a new set of output data quickly and display it to the user--in particular, how many times per second the data can be updated. For many types of programs, especially graphics software and games, the capability of the video subsystem in this area is more important than even the choice of system processor.
  • Capacity: How much information can be presented to the user at one time. This is normally expressed in terms of the resolution of the display in pixels. Common resolutions are 640x480, 800x600, 1024x768 and so on. See the discussion of video card selection for more.
  • Quality: Don't wonder about the importance of video quality unless you also wonder about the importance of your eyes. :^) If you spend a lot of time working on a PC that has poor-quality video, you will probably be an unhappy person regardless of the other attributes of what may be a fine machine.

When designing a PC, you must consider the capabilities of the video card and the monitor simultaneously. Strengths of the monitor only matter if the video card can exploit them, and likewise, the video card cannot be instructed to operate in a way that the monitor can not handle.

However, video card and monitor aren't tied as tightly together as some other components, such as the CPU and motherboard. Fortunately, the interface between regular monitors and video cards is one of the few that actually has remained unchanged over the last many years, allowing most monitors to work with most video cards (although not always optimally.) Matching the components usually is focused on ensuring that the video card and monitor both work at the same resolution and refresh settings, issues related to the "capacity" item above. See the discussion of selecting monitors for more information.

Note: If you are planning to use an LCD screen on a desktop machine, the interface between the video card and monitor becomes something you need to pay more attention to. Some LCD screens work using a standard analog video interface, but others require a special digital connection. See the discussion of notebook components for more.

Next: Storage Subsystem

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