NBTI (Negative Bias Temperature Instability) which can degrade the switching speed of PMOS transistors has become a major reliability challenge. In this paper, we investigate the throughput impact of NBTI on power and thermal-constraint multicore processors and show up to 30% degradation when both process variation and NBIT are considered. Then we evaluate the effectiveness of core rotation, adaptive voltage scaling and adaptive body biasing to improve the throughput of power and thermal constrained multicore processors. Our experimental results demonstrate 11.1% improvement in VDD is sufficient to guarantee throughput after 10-yr NBTI influence when processor variation is not considered. In contract, ABB technique is not able to recover throughput loss caused by NBTI.