In a nutshell, this cable is required for anyone who buys a ATI card supporting Eyefinity Technology and wants to run the extra (3rd) monitor that has only HDMI/DVI inputs
Card below is for the 3 monitor system. Remember, both DVI ports = 1 display each. DVI2 or HDMI maybe used for 2nd display. Display Port is for 3rd display. Normal Display Port cable can be used if the monitor has Display Port connector ONLY. Otherwise, they must buy the above adaptor.
Logitech Extreme 3D Pro Joystick PN 942-000008