One feature that will be a core part of Longhorn graphics is virtualization. In Windows XP, the graphics card is accessed exclusively when running 3D applications. Virtualization allows multiple applications to "time-slice" the graphics hardware. The scheduler manages the command stream traffic to the hardware. Basic driver model LDDM drivers will schedule batches, submitted by the applications—but batches can't be interrupted once started.
The advanced LDDM driver models go one level deeper where batches can be scheduled at the context level. This implies that there's a memory manager, either in software or the graphics hardware, to manage proper context switching. The advanced LDDM allows finer-grain utilization of resources, including system and GPU resources.
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