While normal operation didn't cause any concern, some boards are able to under Voltage this CPU. We set the VCore to 1.1500V with EIST disabled, which works superbly. It doesn't reduce the power-consumption much, it's only some one tenth of a Watt.
The best power/frequency solution is at 3.60GH. Depending on your board, you'll need to set the VCore between 1.2250V and 1.2750V. The DFI board could manage with 1.2250V ,while the ASUS board needed 1.26875V.
Reaching 4GHz is a no brainer, but you need significantly more VCore power compared to 3.60GHz, somewhere between 1.3250V and 1.4000V. We didn't increase any other Voltages, because a decent board should go up to 450MHz FSB without the need of fiddling with NB or VTT Voltages.
Of course, you can increase the FSB to 500MHz, even the MSI P35 board managed to do it, but this time the NB and VTT Voltages needed to be increased.
We also tried to get the most out of the CPU, but if you increase the VCore up to 1.6000V you need a superior air cooling or a water cooling solution. So, 4.40GHz is quite nice for air cooling, isn't it?
We also tested the FSB-wall. It seems our CPU is limited to between 530 and 535MHz. We could reach a stable 530MHz. You don't need to increase the NB and VTT Voltages, but this will, of course, depend on the motherboard. The MSI P35 didn't like to go over 510MHz.