Kurtz, in my case I used this as guidance (This is for eVGA P55 FTW mobo but I'm sure can be applied in any P55 board)
Source
PCIE Frequency Setting to 104MHz. (In some cases this can help maximize BClock)
* QPI Frequency Selection to 4.270 GT/s
* EVGA VDroop Control - Without VDroop
* Bootup CPU VCore - 1.30000V (good for starting point, will likely need to increase for 24/7 stability)
* Eventual CPU VCore - 1.30000V (good for starting point, will likely need to increase for 24/7 stability.)
* DIMM Voltage - 1.65V
* Bootup CPU VTT - 1.400V
* Eventual CPU VTT - 1.400V