@SheldonS: Thanks for the suggestion on Dan Thyer!
To answer some questions- this was a technology demo. The goal was to get a 6x1 Eyefinity 12K-wide setup running at 60 Hz (this was a first).
Regarding the question about windowed mode, no, with Eyefinity this was a single display surface (to Windows) at 11,520 x 2,160. Hard to really describe the experience, you have to see it in real life!