Q:
A: A D-sub is more commonly called a VGA connector. It is analog only and has rather poor high frequency characteristics. DVI comes in three flavors: DVI-D is a digital link. This give a better quality signal. DVI-A is the same signals as a VGA, but the higher quality connector gives a better high frequency performance. DVI-I is the connections for a DVI-D link and a DVI-A link, all in one connector. This is the most common DVI connector for a video card.