twinview: one virtual screen or two?

[Rick Reynolds <rick@rickandviv.net>]

I'm running etch on a D800 laptop.  I have had dual-head display working 
for some time now, using nvidia's 8174 driver.  The dual head display 
worked in a very logical manner, specifically, if a popup dialog was 
centered on the screen it was centered on the screen that was active 
(where the mouse pointer was pointing).  Another indication that it was 
"logical" was that each screen had its own screensaver running.

I've just upgraded to nvidia 8756, and now the screen acts much more 
like one giant screen.  All centered popups are split across the two 
screens.  The screensaver is one large animation across both screens.

I'm wondering where I can read about how dual screen setups interface 
with the window management (I'm running gnome, BTW).  Is there something 
I can tweak to make the two screens behave how I'd like?

Thanks,
Rick Reynolds
--
Never work for a sawmill that's so behind that they don't have time to 
sharpen the blades. -- Will Hayes, Software Engineering Institute