Windows Display Driver Model (WDDM) is the new graphic driver model for video cards running under Windows Vista.
According to Microsoft:
"The Windows Vista desktop is being drawn in a completely different way from all previous versions. Every window will have its own, full window-sized surface to draw to. The desktop will be dynamically composed many times a second from the contents of each window.
The goal for desktop composition is to enable compelling new visual effects for both the Windows user interface and for applications created by third-party developers, all shown on increasingly affordable, high-density displays.
To achieve this enhanced desktop experience, a new display driver model has been designed to radically advance functionality, stability, and reliability. Coupled with acceleration provided by current and future graphics hardware, this new graphics driver model enables Windows Vista to deliver a higher level of performance and quality, and a new desktop experience."
With Windows Vista and a WDDM-supporting GPU, users are no longer required to reboot when the graphics driver is updated. WDDM also provides fault-tolerance against display driver hangs. This enables Windows Vista to detect system hangs and restart the display driver again without the need of a system reboot.
