Why do some graphics cards for PC own two DVI outlets? What would you use the other outlet for?

I hold a custom made PC with 2 ATI Radeon X1600 Pro graphics cards running within crossfire configuration. Each card has two DVI outlets. My 17 monitor have only one DVI inlet. What do you use the further outlets for?

Why do some graphics cards for PC own two DVI outlets? What would you use the other outlet for?

its so you can hook it up to a second monitor if you want. My PC is custom made too and I have a Nvida 6200 LE card it have DVI and a s-video and another out port. I use the DVI to my comp and S-Video to my TV. Its like have two monitors but I use the tv to watch movies from my computer.
they use them for two things:



1. running multiple monitors



2. running roomy high res monitors that own dusl dvi