As the SIMD width of modern microprocessors has been widening for keeping up with the computational demand for HPC systems, recently the vector architecture comes back to spotlight. Besides, a modern vector architecture that has been keeping a large SIMD width and a high B/F ratio has survived and evolved in the HPC community. In this paper, to clarify the potential of the modern vector architecture, we present the performance and power analysis of a modern vector supercomputer SX-ACE using HP-X benchmark programs (HPL, HPCG, and HPGMG). Furthermore, the implementation and optimization of these benchmarks on SX-ACE are discussed. The evaluation results show that SX-ACE achieves the highest efficiencies in the HPGMG and HPCG ranking lists. These facts clearly indicate that the powerful vector processing mechanism with a high B/F ratio is mandatory to achieve a high sustained performance in the future HPC systems.