I doubt it would be possible at that Vcore. Probably closer to 1.4V than 1.3V, even with load line calibration. Once you go over 4ghz, it really starts to lose efficiency fast.
Just because there is 1 core doesn't mean it would run on less. It just has 1/4th the chance of crashing but still required the 1.6v and some extreme cooling.
The intel nehalem architecture has more instructions per clock. So it would beat out a semperon at the same clock rate.