A method and apparatus for adaptively adjusting the 
operating voltage of an 
integrated circuit in response to tester-to-
system variations, worst-case testing techniques, process variations, temperature variations, or reliability wearout mechanisms. The minimum 
operating voltage of an 
integrated circuit is determined either during external testing of the 
integrated circuit or during built-in-self-testing. The minimum 
operating voltage is transmitted to a variable 
voltage regulator where it is used to set the output of the 
regulator. The output of the 
regulator supplies the integrated circuit with its operating 
voltage. This technique enables tailoring of the operating 
voltage of integrated circuits on a part-by-part basis which results in 
power consumption optimization by adapting operating voltage in response to tester-to-
system variations, worst-case testing techniques, process variations, temperature variations or reliability wearout mechanisms. Alternatively, the invention enables adaptive adjustment of the 
operating frequency of an integrated circuit. The invention enables 
system designers to adaptively optimize either system performance or 
power consumption on a part-by-part basis in response to tester-to system variations, worst-case testing techniques, process variations, temperature variations or reliability wearout mechanisms.