The emergence of new applications in high-performance computing is driving the need for more efficient computing machines. As supercomputer architectures become increasingly complex, the combinatorial explosion of design spaces and the time-consuming nature of design simulations lead to challenging design space exploration problems. This work introduces an automated search framework to achieve power-performance-area efficient Arm Neoverse V1 processor designs. Based on multi-objective Bayesian optimization, we propose a new exploration algorithm named SEBO by enhancing the three main stages of the optimization. Experimental results show that SEBO can not only compete with the top state-of-the-art baseline algorithms, but also outperforms them in terms of the quality and diversity of the returned Pareto-optimal designs.