A Hybrid PRAM and STT-RAM Cache Architecture for Extending the Lifetime of PRAM Caches

To extend the lifetime of phase change RAM (PRAM) caches, we propose a hybrid cache architecture that integrates a relatively small capacity of spin transfer torque RAM (STT-RAM) write buffer with a PRAM cache. Our hybrid cache improves the endurance limitation of the PRAM cache by judiciously redirecting the write traffic from an upper memory layer to the STT-RAM write buffer. We have demonstrated through simulation that the proposed hybrid cache outperforms existing write-traffic reduction schemes with the same area overhead. Moreover, our approach is orthogonal to the existing schemes, providing an effective way of investing die area for cache lifetime extension by being used in combination with them.