Systems, methods and program codes are provided for testing multi-core processor chip structures. Individual processor core power supply voltages are provided 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. In one example, a first power supply voltage supplied to a first processing core differs from a second core power supply voltage supplied to a second processing core, both cores operating in compliance with a reference clock rate specification. Core power supply voltages may be selected from ordered discrete supply voltages derived by progressively raising or lowering a first supply voltage, optionally wherein the selected supply voltage also enables the core to operate within another performance specification.