The proposed Level-3 Trigger System for STAR ============================================= C. Adler, J. Berger, D. Flierl, J. S. Lange, D. Schmischke, R. Stock, Ch. Struck University of Frankfurt, Germany D. Roehrich University of Bergen, Norway J. Landgraf, M. J. Levine, A. Ljubicic,Jr., M. Schulz BNL Brookhaven, US V. Lindenstruth University of Heidelberg, Germany M. Demello, P. Yepes Rice University, Houston, US J. J. Schambach University of Texas, Austin, US The STAR detector at RHIC/BNL Brookhaven will start in 1999 to investigate heavy ion and p-p collisions with up to T(beam)=100 GeV/nucleon. One of the main research goals is the search for the quark-gluon plasma. The proposed level-3 trigger system is an event filter farm, consisting of fast, cheap processors (in the first implementation 24 Pentium II or ALPHA), using data of the 24 STAR TPC (time projection chamber) sectors. The accepted fraction will be ~1/100 of the digitized event rate, with a goal trigger rate of R=100 Hz. The level-3 software includes (a) an online TPC cluster finder task on 432 Intel i960s, (b) an online TPC track finder task on the level-3 farm (expected ~8000 tracks per central Au-Au collision) and (c) an event selection task. One of the most important applications will be the online invariant mass reconstruction of J/Psi->e+e- in Au-Au collisions, as J/Psi suppression is commonly regarded as one the the most promising signatures of the quark-gluon plasma. Results of a prototype system (Pentium II 450 MHz with DOLPHIN(tm) SCI-PCI interface) concerning (a) tracking efficiency and timing and (b) SCI latency will be shown.