Automatic voltage regulation for processors having different voltage requirements and unified or split voltage planes

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. If it is of a split voltage plane type, the switching circuit applies the output of the fixed-voltage power supply to an I/O voltage plane of the processor, with the programmable power supply being first set to generate a voltage determined by whether a second grounded pin is present in the processor. Then, an instruction in an initialization program causes the processor having a split voltage plane to transmit an identification code, which is used to determine a final level of the programmable power supply voltage.