Video, Sound, Modems, and Network Adapters
Video Overview
Video is the single most important feature of a PC. Even in the two situations that don't require video, servers and blind people's computers, video is still essential. In the case of servers that aren't regularly accessed by users, you still need video on occasion for configuration, repair, and other operations. Blind people use screen readers and keyboards to use their computers, but screen readers don't work until the OS boots. Consequently, repairs and other operations often require a sighted technician to see the monitor. It is because of video's high level of importance that the BIOS allows the video adapter to provide base VGA video as soon as the computer is powered on. Base video is enough for clear text: 640 x 480 pixels (the smallest picture elements) and 16 colors. Video Graphics Adapter (VGA) is a video standard used by PCs for many years. Super VGA (SVGA) is a major improvement, but it is based on VGA and the monitor connectors are the same. (See the end of Chapter 3, "Motherboards and Their Components," for more information on ports.) Figure 8.1 shows a monitor plug and a corresponding VGA connector.
Figure 8.1: VGA connectors.
Video Adapter (Graphics Adapter, Video Card) Overview
Many computers come with video built into the motherboard. However, many motherboards don't have built-in video, and some that do also have AGP slots for additional or replacement video adapters. There are also PCI video adapters available, although PCI isn't considered the best interface for video. There are several reasons to use separate video adapters:
Users may want better video performance than their motherboard provides.
If built-in video fails or is troublesome, it can be disabled in the BIOS and an expansion card used.
Note Sometimes, inserting an expansion video card automatically disables built-in video in the BIOS.
Users might need to use two or more monitors simultaneously, and multiple adapters or a specially designed video adapter is necessary for two or more monitors. Recent Windows versions support multiple monitors for different purposes, including having all monitors show the same screen, having one screen spread across more than one monitor, or even having a different screen on each monitor. For more information on multiple monitors in Windows XP, search Windows XP's Help and Support for "multiple monitors."
Note Dualview in XP is similar to multiple monitors, but works with laptop/notesite computers. With Dualview, the laptop's built-in screen is the primary monitor, and a monitor that the user attaches to the external VGA port is the secondary monitor. For more information on Dualview, search for it in XP's Help and Support.
As covered in Chapter 3, there are also DVO header connectors for DVI digital video adapters in some motherboards, and built-in DVI ports in others. As of the time of this writing, most PC motherboards have either built-in VGA ports or AGP slots for VGA video cards. Digital video capability might or might not be present.
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