In this paper, we propose PDRAM, a novel energy efficient main memory architecture based on phase change random access memory (PRAM) and DRAM. The paper explores the challenges involved in incorporating PRAM into the main memory hierarchy of computing systems, and proposes a low overhead hybrid hardwaresoftware solution for managing it. Our experimental results indicate that our solution is able to achieve average energy savings of 30% at negligible overhead over conventional memory architectures. Categories and Subject Descriptors B.7.1 [Integrated Circuits]: Memory Technologies General Terms Design, Experimentation, Performance Keywords Phase Change Memory, Energy Efficiency, Memory management