This paper introduces a large-scale parallel MC-DSP prototype, PolyDSP constructed with heterogeneous super-nodes, and proposes a data speculation technique based on customized data streams transmission control engine (DSTCE). This technique implements high efficient data streams transmissions among different data ports within a super-node and transmissions between neighbor super-nodes. The superiority of this technique is that it can combine a data speculation solution with the programming model of PolyDSP, avoid complex cache coherence problems, thus improving the parallelism between data processing and memory accessing for MC-DSPs significantly. Our simulation results show that, the performance of single super-node of PolyDSP is improved by 22% on average, and the performance of PolyDSP based on DSTCE is 14% higher than that of PolyDSP based on CC-NUMA structure with two super-nodes.