I have already tested everything (including almost bare MOBO) but even if running with only cpu and ram i get the same:
if graphic card removed boots fine (i can access via ssh, all cpu cores recognised, fast boot and everything ok), but if i plug the card i get the slow bios boot (hardware check screen is very slow, prints letter by letter so it takes a lot of time to perform boot check and start running the os (or giving disk error if testing with minimum components).
Few random tries boots without problem with the GPU plunged, so i hope its a fixable damage, but i hadn't determined yet whats the source of this problem.
Any recommendable test to perform and discard possible issues?