LostCircuits posted a review on the Phenom II X4 810 and X3 720 Black Edition

The Phenom X3 II 720 is being sold as Black Edition, meaning that the multiplier is completely unlocked, in short, an invitation for overclocking. In fact, as it turned out, I have never seen a CPU that easy to overclock out of the box without doing anything beyond moving a few sliders on AMD's OverDrive utiliy. Set the core voltage to 1.45V, the NB to 1.325 V with a 1.235 V value for the HT interface and push the multiplier all the way to 20 x. Twenty seconds later, CPUZ showed that we were running at 4.0 GHz. 4.1 GHz caused some problems. Either setting was done with standard air cooling and at room temperature. Granted, there were a few stability problems even at 4.0 GHz but at 3.8 GHz, the X3 720 was purring along no matter what we threw at it to get 372 fps average in F.E.A.R. and 170 fps average in Crysis. Without any hiccup.

Phenom II X4 810 and X3 720 Black Edition Review