Having two monitors plugged in - affects performance?

[Duvan]

I have a graphics card with a S-video port and two DVI ports.
I've got two screens plugged into the two DVI:s...
I thought that u could disable one of the monitors in the ATI program but it seems the second monitor is still showing a picture... Normally just a zoomed in version of my primary monitor's screen... but when I play games it is often identical to my primary screen.
Does this affect performance? I.e. lower FPS etc.
What if I've got the monitor set up in ATI as a extended desktop, or clone desktop... does this affect performance in games?

 

[Duvan]

Thanks. Did work after trying it two times

Okay, so it does affect performance in other words?

 

[Duvan]

Okay. So having "clone screen" or something like that affects performance less than extended desktop (if running somethin else on the secondary screen)?