The performance of a microelectronic circuit can be configured by making an operating parameter assume an operating parameter value. An operating method comprises selectively setting the microelectronic circuit into a test mode that differs from a normal operating mode of the microelectronic circuit, and utilizing said test mode to input test input signals consisting of test input values into one or more adaptive processing paths within the microelectronic circuit. An adaptive processing path comprises processing logic and register circuits configured to produce output values from input values input to them. The performance of such an adaptive processing path can be configured by making an operating parameter assume an operating parameter value. The method comprises making said one or more adaptive processing paths form test output values on the basis of the respective test input values input to them, and forming a set of test output signals by collecting said test output values given by said one or more adaptive processing paths. The method comprises examining said set of test output signals, and forming a test result on the basis of said examining, and using said test result to select and set an operating parameter value for said operating parameter.