How can you say that the DVI port on motherboard is not working? Have you checked it!!
If there is display problem, you can try these options also:-
a) Replace your CPU to monitor cable with another working cable.
b) Check your RAM.
c) Check your graphics card.
d) BGA chip can also be a problem(for display issues).
DVI port on monitor's side can also be a problem.
Check your whole CPU with another monitor with same cable.