Abstract: Apparatus for providing electrical power to a processor (CPU) within a computing system includes a fixed-voltage power supply and a programmable power supply. When the computing system is turned on, a switching circuit determines whether the processor is a unified voltage plane type, having a first particular pin electrically floating, or a split voltage plane type, having this pin grounded. In either case, the output of the programmable power supply is applied to the pins associated with the core voltage plane of a split voltage plane type. If the processor is a unified voltage plane type, the switching circuit applies the output of the programmable power supply to the pins associated with the I/O voltage plane of a split voltage plane type.