Power grid structure to optimize performance of a multiple core processor

A reduced number of voltage regulator modules provides a reduced number of supply voltages to the package. The package includes a voltage plane for each of the voltage regulator modules. Each core or other component on the die is tied to a switch on the package, and each switch is electrically connected to all of the voltage planes. A wafer-level test determines a voltage that optimizes performance of each core or other component. Given these voltage values, an engineer may determine voltage settings for the voltage regulator modules and which cores are to be connected to which voltage regulator modules. A database stores voltage setting data, such as the optimal voltage for each component, switch values, or voltage settings for each voltage regulator module. An engineering wire may permanently set each switch to customize the voltage supply to each core or other component.