Multiple instances of Viz Engine can be spawned along multiple graphic cards. The assignment of the GPU to be used is done automatically, only the number of the instance needs to be set by the startup parameter -u1, -u2 etc..
Some example use cases:
Two Program Outputs: Using two instances that can run two program channels (for example, one for SD and one for HD output).
One Program Output and One Preview Output: Running a control application with one instance for preview and one instance for program output with video. Ideal for outside broadcast environments.
One Program Output for Stereoscopy: Producing graphics composited for stereoscopic use. In addition, this also saves rack unit space as all hardware is installed into one machine.
Multiple frame servers on one machine.
Note: The limitations to such systems (in general and not limited to Vizrt systems alone) are memory usage, access and a lack of power redundancy. Also keep in mind that the memory usage of each machine needs to be covered by the system (for example, two P6000 with 24GB of texture memory require a machine with at least 48GB).