How might GPU companies tell that a card is overvolted?

[wannaturnuptheheat]

I have a question about companies that offer "OC-approved" warranties that allow clock modification but specifically disallow overvolting on video cards.

How can they tell? Does the graphics card have a CMOS that they can recover? Is there some bit of circuitry that... I dunno, 'goes off' (I'm kind of naive with regards to circuit mechanics) if it's overvolted?

Or do they just assume that all 'fried' cards were overvolted?

 

[iam2thecrowe]

i assume they have no idea weather or not its been overvolted. but if its a gtx570 or gtx590 they will know, as they explode when overvolted.