An Evaluation of the ORNL Cray XT3

In 2005, Oak Ridge National Laboratory received delivery of a 5,294 processor Cray XT3. The XT3 is Cray’s third-generation massively parallel processing system. The ORNL system uses a singleprocessor node built around the AMD Opteron and uses a custom chip—called SeaStar—for interprocessor communication. The system uses a lightweight operating system called Catamount on its compute nodes. This paper provides a performance evaluation of the Cray XT3, including measurements for microbenchmark, kernel, and application benchmarks. In particular, we provide performance results for strategic Department of Energy applications areas including climate, biology, astrophysics, combustion, and fusion. Our results, on up to 4,096 processors, demonstrate that the Cray XT3 provides competitive processor performance, high interconnect bandwidth, and high parallel efficiency on a diverse application workload, typical in the DOE Office of Science.