The aim of our work is to investigate the performance and overall scalability of an optimistic discrete-event simulator on a Blue Gene/L supercomputer. We find that strong scaling out to 16,384 processors is possible. In terms of event-rate, we observed 853 million events per second on 16,384 processors for the PHOLD benchmark. This is 1.5 times faster than any previously reported PDES synchronization protocol for PHOLD executing on a Blue Gen/L supercomputer (e.g. conservative, optimistic or hybrid). Additionally, we observed 2.47 billion events per second for a PCS telephone network model when executed on 32,768 processors. To the best of our knowledge, this is the first multi-billion event rate achieved for any Time Warp model executing on a Blue Gene/L supercomputer.