The scheduling of sporadic task systems upon multipro- cessor platforms is considered, when inter-processor migra- tion is permitted. It is known that current schedulability tests for such systems perform quite poorly when compared to schedulability tests for partitioned scheduling. Limita- tions of current tests are identified, which may be responsi- ble for the unsatisfactory performance of these tests. A new test that overcomes some of these limitations is proposed and proved correct.