The Sporadic Server (SS) overcomes the major limitations of other Resource Reservation Fixed Priority based techniques, but it also presents some drawbacks, mainly related to an increased scheduling overhead and a not so efficient behavior during overrun situations. In this paper we introduce and prove the effectiveness of an improved SS with reduced overhead and fairer handling of server overrun situations. We also show how this can be efficiently exploited to provide temporal isolation in a multiprocessor platform, adapting already existing schedulability tests. Categories and Subject Descriptors D.4.1 [Operating Systems]: Process Management Keywords Scheduling, Fixed Priority, Multiprocessor, Sporadic Server, Overruns