Advanced accelerator simulations have played a prominent role in the design and analysis of modern accelerators. Given that accelerator simulations are computational intensive and various high-end clusters are available for such simulations, it is imperative to study the performance and scalability of accelerator simulations on different production systems. In this paper, we examine the performance and scaling behavior of a DOE SciDAC funded accelerator simulation package called Synergia on three different TOP500 clusters including an IA32 Linux Cluster, an IA64 Linux Cluster, and a SGI Altix 3700 system. The main objective is to understand the impact of different high-end architectures and message layers on the performance of accelerator simulations. Experiments show that IA32 using single-CPU can provide the best performance and scalability, while SGI Altix and IA32 using dual-CPU do not scale past 128 and 256 CPUs respectively. Our analysis also indicates that the existing accelerator simulations have several performance bottlenecks which prevent accelerator simulations to take full advantage of the capabilities provided by teraflop and beyond systems.