The Tahiti XT GPU is factory-overclocked at 1000MHz (ref: 925MHz). The card comes with two 8-pin power connectors (ref: one 8-pin and one 6-pin) allowing a total of 375W of maximum power consumption. With its strong power circuitry, this card is ready for massive overclocking!
Here are the detailed specs (from TPU):
Update (2012.01.23): First Look: ASUS Radeon HD 7970 DirectCU II Top Video Card