I have a machine with two NVIDIA 8800 GTXs. Each card has two DVI outputs, and the computer is driving four monitors in total.

I currently have each display set up as a separate X screen with xinerama enabled, and I have a working four-monitor desktop setup in a 2x2 arrangement. However, because each display constitutes a separate screen, when I do something like maximize a window, it only fills the one monitor.

I'd really like Ubuntu to treat all of my monitors as one giant screen instead of distinguishing between separate displays (i.e., if I maximize something, it would stretch across all the monitors). It seems like Twinview is designed to do this, but I haven't heard about using it for anything other than two outputs on the same video card. I want to link four monitors that are plugged into two video cards. Is this possible?