Enhanced Support for Dual Monitors

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Multimonitor support in Windows Vista is yet another enhanced area for Windows. The new Windows Display Driver Model (WDDM) is a new graphic driver model for video cards running Windows Vista and (under the hood) the desktop is being drawn in a very new way as compared to previous versions of Windows. For details, see WDDM in the MSDN Library.

In Windows NT, there was no built in support, but vendors could write customized drivers and utilities to get the job done. In Windows 2000, some native support was introduced and Windows XP provided support for multiple graphics cards natively via the Windows XP Display Driver Model (XPDM). In Vista, these older XPDM drivers will still work using legacy graphics code. With Vista, there are significant new management options for handling multiple adapters and displays. One thing this new configuration will not support is the use of multiple graphics cards using multiple drivesr on the same PC (such as two from different manufacturers).

To take advantage of WDDM, all graphics adapters in a system must use the same driver type: either XPDM (XP) or WDDM (Vista). Further, if you have two graphics adapters on a system, they must both use the same WDDM driver. So, if both adapters do not offer WDDM drivers, you will need to install the XPDM driver for each device to get multimonitor support as it was in XP. The ideal situation though, is to choose adapters that use the same WDDM driver; adapters from the same ASIC (Application-Specific Integrated Circuit) family normally have the same driver. WDDM support is generally available for newer hardware (2006 and later).

For WDDM Vista drivers, two monitors (dual-view) via a single graphics adapter with two outputs like DVI and VGA) are natively supported. For two three or more monitors the following configurations are supported:

* A mobile PC with an internal graphics adapter A, connected to a docking station that includes an external graphics adapter B. Both the internal graphics adapter A and the external graphics adapter B must use the same WDDM driver.
* Graphics adapter A with two outputs in an AGP slot, plus another graphics adapter B with one or more outputs in a conventional PCI slot. However, both A and B must use the same WDDM driver.
* Graphics adapter A with two outputs in an x16 PCIe slot, plus another graphics adapter B with one or more outputs in an x1 PCIe, another x16 PCIe, or a conventional PCI slot. Once again, both A and B must use the same WDDM driver.