drives two walls with a single PC and an nVidia graphics card

[Jeff]

If you're running the CAVE on a single machine you can specify a Vizard window to draw each wall to rather than a master or client machine. If you take a look at the <vizcave:Cave>.addWall documentation this will be more clear. You can create a subwindow that takes up half the screen and place that next to Vizard's MainWindow, one for each wall.

You can also try using clustering on a single machine if you have the Enterprise version of Vizard. For this, check localhost in the cluster master utility. There is a count field where you can specify the number of clients. If you leave that number at 1 there will be two graphics windows created.