I am already using the bottom right socket for my main monitor.To add another monitor to the other DVI socket I need the same cable cause from what I see in the image the 2 dvi differ a bit (one has a cross with 4 little holes and the other has only one line) ?
The "cross with 4 little holes" caries the analog vga signal. That's for the DVI-to-VGA cable. The second dvi port is a digital port only. DVI-to-DVI cables dont have pins for the holes and will fit in the second port.