This paper focuses on a performance of network-on-a-chip (NoC) and I/O of ClearSpeed's CSX600 coprocessor with 96 multithread processing elements. Two versions of the Himeno Benchmark were implemented on the CSX600 to evaluate its performance when it encounters frequent memory transfers between shared and local memories, or between local memories. In order to efficiently use the NoC bandwidth, the dataflow was customized to the one-dimensional array structure of CSX600's NoC. The results of evaluation and profiling indicate that the performance was lower than 1/50 of the sustained performance. We show three key points to improve the performance on such a case: 1) exploiting bandwidth between mono and poly memory, 2) further program tuning, and 3) architectural reform.