Overclocking Without Increasing Voltage
Multiplier 28x, 3.73 GHz (Turbo Boost 29x, 30x at 3.86, 4.00 GHz)
All frequency settings right up to a 28x multiplier, yielding a 3.73 GHz clock speed, run perfectly at default voltage. It's even possible to decrease Vcore a bit, if you're looking to reduce power consumption. Most people willing to fork out $999 on a processor will probably want to leave themselves some extra overhead, though, so we left the voltage alone. Since no voltage tweak is necessary at 3.73 GHz, we found this setting almost as efficient as the next one.
Multiplier 29x, 3.86 GHz (Turbo Boost 30x, 31x at 4.00, 4.13 GHz)
This setting still works reliably without any voltage increase. In any case, 3.86 GHz is the line at which you have to apply more voltage to reach higher clocks (on this particular sample, that is).