Addressing Read-Disturbance Issue in STT-RAM by Data Compression and Selective Duplication

In deep sub-micron region, spin transfer torque RAM (STT-RAM) shows read-disturbance error (RDE) which presents a crucial reliability challenge. We present SHIELD, a technique to mitigate RDE in STT-RAM last level caches (LLCs). SHIELD uses data compression to reduce cache-write traffic and restore requirement. Also, SHIELD keeps two copies of data blocks compressed to less than half the block size and since several LLC blocks are only accessed once, this approach avoids several restore operations. SHIELD consumes smaller energy than two previous RDE-mitigation techniques, namely high-current restore required read (HCRR, also called restore-after-read) and low-current long latency read (LCLL) and even an ideal RDE-free STT-RAM cache.