楼主故意不读测试报告？
The SPE versus PPE performance gap is huge. Measuring the exact SPE performance shows that one SPE runs at more than 11 times the speed of the PPE and at more than twice the speed of the P4. Figure 6A shows a 1.5 times speedup for one SPE, which indicates that even with one SPE, the PPE is a major drag on performance. This is despite the fact that most of the PPE integration code is run in parallel on the SPE. The PPE overhead in this benchmark is mostly due to packing and unpacking SPE workloads, although there is some small overhead for SPE scheduling. The multi-SPE scheduling is less than optimal, as well. The multi-SPE performance continues to scale until the PPE overhead dominates at around three or four SPEs.

单颗SPE的性能在1.5x p4以上。2颗spe再多以后性能没有线性上升是因为调度瓶颈，应该是可以通过程序优化缓解的。。