We already reported the overclocking features of Sandy Bridge-E, whose announcement will take place next week.
Sandy Bridge-E processor overclocking with stock cooling, hardly will differs from the default , it can be overclocked to 4.5 GHz with water cooling system.
The high heat dissipation of Sandy Bridge-E has forced Intel to implement a fairly aggressive defense mechanisms, known as throttling. If LGA 1155 limiting temperature was equal to 98 degrees Celsius, then Sandy Bridge-E processor LGA 2011 threshold was reduced to 86 degrees Celsius.
CPU-Z screenshot can show a frequency of 4.5 GHz, but under load in any test, its frequency is not so high. The processor will reduce the frequency as long as the current temperature is reduced to no greater than 86 degrees Celsius. Perhaps a new stepping Sandy Bridge-E will change the situation with overclocking.