A computer implemented method, data processing system, and computer usable code are provided for testing multi-core microprocessors. A test process initiates testing on communication bus interfaces associated with a set of processor cores on the multiprocessor in which the communication bus interfaces are disabled and wherein the testing uses a set of isolation test sequences to obtain results. The process identifies a set of functional processor cores in the set of processor cores based upon the results. The process also initiates a ramp logic built-in self-test to test a ramp associated with a functional processor core in the set of functional processor cores, wherein the ramp logic built-in self-test determines if the communication bus interface associated with functional processor core in the set of functional processor cores is functional.