Exploiting narrow-width values for improving non-volatile cache lifetime

Due to the high cell density, low leakage power consumption, and less vulnerability to soft errors, non-volatile memory technologies are among the most promising alternatives for replacing the traditional DRAM and SRAM technologies used in implementing main memory and caches in the modern microprocessor. However, one of the difficulties is the limited write endurance of most non-volatile memory technologies. In this paper, we propose to exploit the narrow-width values to improve the lifetime of non-volatile last level caches. Leading zeros masking scheme is first proposed to reduce the write stress to the upper half of the narrow-width data. To balance the write variations between the upper half and the lower half of the narrow-width data, two swap schemes, the swap on write (SW) and swap on replacement (SRepl), are proposed. To further reduce the write stress to non-volatile caches, we adopt two optimization schemes, the multiple dirty bit (MDB) and read before write (RBW), to improve their lifetime. Our experimental results show that by combining all our proposed schemes, the lifetime of non-volatile caches can be improved by 245% on average.