More Core Voltage
At 1.250V, the default core voltage of the Core 2 Extreme QX9775 CPUs was slightly higher than that of the QX9770 desktop model. At the same speed, the desktop part uses a slightly lower core voltage.
Compared to the desktop CPU, which is practically identical to the new Skulltrail parts, Intel has raised the core voltage by 0.075 Volts. Nonetheless, the QX9775 offers better overclocking potential.