TriZone: A Design of MLC STT-RAM Cache for Combined Performance, Energy, and Reliability Optimizations


Journal Article

© 2017 IEEE. Spin-transfer torque random access memory (STT-RAM) is a promising technology for future nonvolatile caches and memories. To increase the storage density, multilevel cell (MLC) technique was recently introduced to STT-RAM designs at the cost of degraded access speed, reliability, and energy efficiency. Existing MLC STT-RAM cache architectures primarily focus on the performance and energy optimizations but ignore the crucial demand for reliability. In this paper, we propose 'TriZone' - a holistic design scheme for MLC STT-RAM cache to simultaneously meet the requirements of performance, energy, and reliability. Three cache block configurations, namely hard, soft, and mixed, are constructed with the hard-bit, soft-bit, and both hard-bit and soft-bit of MLC STT-RAM, respectively. By observing the difference of these cache blocks, a nonuniform strength ECC (NUS-ECC) is developed to guarantee the operational reliability of a cache block with a variable decoding delay adapting to the needs of error correction (e.g., the number of the erroneous bits). The whole MLC STT-RAM cache is then partitioned into three regions, each of which is composed of different cache blocks. In order to achieve the best tradeoff among performance, energy, and reliability, we then introduce the dynamic cache partitioning to determine the partition of this tri-way MLC STT-RAM cache according to the runtime characteristic of various applications. Experiment results show that compared with conventional performance-driven MLC STT-RAM cache design with pessimistic ECC, TriZone can improve the system performance and energy by averagely 11.7% (10.0%) and 13.3% (15.7%), respectively, for single-threaded (multiprogram) applications. The additional area overhead associated with NUS-ECC is limited by 3%.

Full Text

Duke Authors

Cited Authors

  • Liu, Z; Mao, M; Liu, T; Wang, X; Wen, W; Chen, Y; Li, H; Wang, D; Pei, Y; Ge, N

Published Date

  • October 1, 2018

Published In

Volume / Issue

  • 37 / 10

Start / End Page

  • 1985 - 1998

International Standard Serial Number (ISSN)

  • 0278-0070

Digital Object Identifier (DOI)

  • 10.1109/TCAD.2017.2783860

Citation Source

  • Scopus