Reason why the graph is so skewed.. 1.61v for 4.5GHz is garbage. My E8400 did 4GHz with 1.3825v, 4.5Ghz with 1.45v, 4.7GHz with 1.47v and walled at 540FSB. I have seen many E8400's doing 4.5GHz with sub 1.5v. Blasting 1.6v through that chip is a sure-fire way to kill it. If you ask for screenies or declare my thoughts as fake, I bought the chip on a whim, benched it once, put it in a drawer, and subsequently sold it, so take my words on faith. 1.6v will kill your chip.

edit: ps.. I had a "mediocre" E8400 compared to alot of other samples just to put it in perspective.