Described is an apparatus comprising: first and second processing cores; and a PCU which is operable to: generate a first VID for an off-die regulator external to the apparatus, the first VID resulting in a first power supply for the first processing core; and generate a second VID different from the first VID, the second VID resulting in a second power supply for the second processing core. Described is an apparatus comprising: a plurality of power-gate transistors controllable by a digital bus, the plurality of power-gate transistors operable to provide a first power supply to a processing core, and to receive a second power supply as input; an ADC to receive the first power supply and to generate a digital output representative of the first power supply; and a controller to receive the digital output representative and to generate the digital bus for controlling the plurality of power-gate transistors.