Is it the computer or the monitor?

I use DVI to connect my dell pc to my dell monitor. When I try to connect with hdmi though i get that thin black bar around the outside of the picture. Same thing when I try to connect my pc to my tv. Im about to go buy a thunderbolt display connector for my macbook and was wondering if I get hdmi will it have that little black bar around the outside if I connect it to my dell monitor or my tv? Is it the monitor doin that or is it the pc not supporting resolutions correctly? What exactly is making it do that?

Have you tried different resolutions?

its called underscan. you need to look for overscan adjustments. dont know of a fix myself. (i do on a windows, though.) have a look in display prefs.

long story short, its the computer. The graphics card to be particular. thats not to say its faulty. ites perfectly fine.