Enhanced Multi-Monitor Support: Dualview
Although multi-monitor support is not new to Windows—it was first introduced with Windows 98, and extended in Windows 2000—Windows XP enhances this technology with Dualview, which provides additional display configuration options for mobile and desktop computers.
Dualview is an extension to the multiple monitor support built into Windows 98, Windows Me, and Windows 2000. Some high-end display adapters and many mobile computers support two or more monitor interfaces to the same display adapter. Dualview enables all the interfaces to display different outputs at the same time. For example, on a mobile computer, you can connect a monitor and use both the mobile computer display and the external monitor to expand your desktop space. Or, if you are using your mobile computer for a presentation, you can use the mobile computer display to look up data or documents, without interfering with the presentation on the second monitor.
The technology is relatively straightforward. The driver for the display adapter registers with the operating system two or more distinct instances of the same display adapter (depending on the number of outputs built into it)—one for the first video output port, and one for each subsequent output port. Figure 5 below shows a compatible display adapter used in a Dualview configuration.
F
igure 5. Dualview is enabled on a compatible display adapter in the Settings tab of the Display Properties dialog box.
Dualview is thus very similar to the multi-monitor feature, but has an added advantage in that it does not require updating the BIOS to disable VGA on secondary devices. On a portable computer, the primary monitor is always the LCD display screen and cannot be changed. On a desktop computer, you may select the primary monitor, which by default is the monitor attached to the first video output port. Dualview can be used with docked or undocked portable computers; Windows XP does not, however, support hot-undocking of portable computers that have an active multi-monitor configuration.
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