Systems, methods and program codes are provided for selectively adjusting multi-core processor chip structure individual processor core power supply voltages through controlling individual power supplies for each core, in one aspect to ensure that one or more cores operate at clock rates in compliance with one or more performance specifications. Nominal power supply voltage is supplied to a first processing core, and a second core power supply voltage greater or lower than the nominal power supply voltage is supplied to a second processing core, both cores operating in compliance with a reference clock rate specification. The second power supply voltage may be selected from ordered discrete supply voltages derived by progressively lowering the nominal supply voltage, optionally wherein the selected supply voltage also enables the second core to operate within another performance specification.