In order to get a higher switching speed of a transistor you need to increase the voltage. For the power usage of an electronic device holds: P = V^2 / R, therefore if you want a higher clock frequency your power usage increases with the square of the applied voltage. Which means that you'll need excessive amounts of cooling power (e.g. LN2) to keep your CPU from dying at such high core voltages (2V). Usually processors are run at ~1.2V for factory specs.