can xrandr "split" a 2560x1024 screen into two separate 1280x1024 screens?

[Lara Michaels]

Hi everyone,

I know how to use xrandr to position screens relative to each other when I have two monitors plugged into my computer, but now I need something else. Any help is much appreciated:

Can I use xrandr to split (what it thinks is) a 2560x1024 screen into two separate monitors? I am using a Matrox Dualhead2go, which connects into my laptop and presents itself to the video card as a very wide 2560x1024 screen.

I need to do this so that, eg, maximizing a window to "full screen" maximizes to be 1280x1024, rather than spanning it over the entire two screens. 

Thank you for any help!

~lara