Transactional memory is an appealing technology which frees programmer from lock-based programming. However, most of current hardware transactional memory systems are proposed for multi-core processors, and may face some challenges with the increasing of processor cores in many-core systems, such as inefficient utilization of transactional buffers, unsolved problem of transactional buffer overflow, etc. This paper proposes PM_TM, a hardware transactional memory for many-core processors. The system turns transactional buffers that are traditionally private to processor cores into shared by moving them from L1-level to L2-level, and uses partition mechanism to provide logically independent and dynamically expandable transactional buffers to transactional threads. As the result, the solution can utilize transactional buffers more efficient and moderate the problem of transactional buffer overflow. The system is simulated and evaluated using gems and simics simulator with STAMP benchmarks. Evaluation results show that the system achieves better performance and scalability than traditional solutions in many-core processors.