mine will do 4.7 stable, well under 1.3V. no need to run it that fast. as in it destroys any and every task you put in front of it (even at stock). but if you "just want to see" what it will do, GO FOR IT.
i run mine daily at 4 (very low stock voltage) or 4.4ghz (under 1.165V) and it lays to waste anything i can put it to work on.