Comparison of Cray XT 3 and XT 4 Scalability ∗

The Cray XT3 and XT4 have similar architectures, differing primarily in memory performance and in bandwidth between the node and interconnect. This paper evaluates and compares the scalability of the XT3 and XT4. Kernel benchmarks are used to verify and to quantify the performance differences between the systems. Application benchmarks are used to examine the impact of these differences on scalability. Both kernel and application benchmarks are used to identify how to use the systems most