When we popped the heatsink off, we found a radically reworked PCB.
6+2 phase power with Super Alloy chokes
ASUS's propietary DIGI+ VRM controller that is also found on their other boards
Implacable quality of the resistors and soldering
Eight of Hynix's H5GQ1H24AFR-R0C GDDR5 memory chips clocked at 1.5GHz make up the 2GB of frame buffer.
The 28nm TSMC made GK104 Kepler, although not as GP compute friendly (dismal 1/32 DP ratio) as its direct AMD Taihiti competitor, is an efficiency monster when it comes to 3D benchmarks and gaming. Actual frequency headroom varies with voltage and the quality of the ASIC, but generally we should be able to hit 1.2-1.35GHz with conventional cooling and near 2GHz with subzero.
ASUS have deployed their DirectCU II coolers in their non-reference offerings for quite some time now, albeit with slight variations. They all incorporate Heatpipe Direct Touch (HDT) technology and PWM enabled fans to ramp up the airflow when neccessary.