A low-power hybrid magnetic cache architecture exploiting narrow-width values

Modern microprocessors have increased the word width to 64-bits to support larger main memory sizes. It has been observed that data can often be represented by relatively few bits, so-called narrow-width values. To leverage narrow-width data, we propose a hybrid cache architecture composed of magnetic RAM (MRAM) and SRAM to save the upper and lower 32-bits of each word in MRAM and SRAM respectively. To address write performance issue of MRAM, we propose an optimal dynamic write buffer (DWB) allocation mechanism. To enhance efficacy of our hybrid cache in the absence of narrow-width values, we propose a double row write (DRW) technique that adaptively partitions non-narrow data to two 32-bit pieces for consecutive row writes in the SRAM part. DWB and DRW jointly guarantee the performance of the proposed hybrid cache and balance a tradeoff between the buffer size and the number of double row writes. Our evaluation on SPEC CPU2000, SPEC CPU2006 and Mibench benchmarks shows that our hybrid cache can achieve up to 46% power and 24% area savings at the same performance as the conventional SRAM cache.