三维堆叠DRAM的低功耗刷新技术研究

项目名称： 三维堆叠DRAM的低功耗刷新技术研究

项目编号： No.61504153

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 无线电电子学、电信技术

项目作者： 王颖

作者单位： 中国科学院计算技术研究所

项目金额： 21万元

中文摘要： 三维堆叠DRAM的发展有效地满足了计算机系统日益增长的存储空间与带宽需求，是存储器发展的重要方向。然而，三维DRAM的刷新功耗开销由于三维芯片高温漏电问题变得越来越大。本项目主要研究面向三维堆叠DRAM的低功耗刷新技术，并计划从物理电路层、结构层与系统层多个角度出发，提出跨层的三维堆叠DRAM刷新控制与优化方法。首先，在电路层，利用片间TSV连线与DRAM冗余重映射，修复快速漏电单元，提高最小刷新间隔。然后，在结构层，通过存储数据感知与温度自适应的刷新频率调整，减少刷新次数。最后，在系统层，利用包含多媒体、机器学习与数据挖掘在内的近似计算应用的故障容忍能力，降低非关键存储区域的刷新频率。通过电路层、结构层与系统层的跨层协同优化，提出包括弱单元修复、环境自适应刷新、非精确刷新在内的多项创新方法，保证三维DRAM系统性能与可靠性的同时，探索三维DRAM刷新功耗下限，提升计算机系统的整体效能。

中文关键词： 三维堆叠；动态随机访问存储器；硅通孔；低功耗；DRAM刷新

英文摘要： Three-Dimensional （3D）stacked DRAM is developed to meet the computing systems’ increasing demand for the memory capacity and bandwidth, and it is thought as a trendy design paradigm for future memory system. However, because of the high storage density and thermal dissipation density, the cost of refresh operations in 3D stacked DRAM keeps rising to compensate the leakage and guarantee data integrity in memory. This proposal focuses on the low power refresh technology for 3D stacked DRAMs, and aims to reduce the power cost induced by refresh operations. In general, we propose coordinated solutions to solve the refresh power issue in 3D stacked DRAMs from circuit level, architectural level and system level. First, we use TSVs and inter-die remapping techniques to repair the leakiest cells and raise the lowest refresh interval for DRAM arrays. Second, we propose the content-aware and temperature-adaptive refresh rate tuning strategy to eliminate unnecessary refresh operations. Third, we exploit the intrinsic retention-fault tolerance ability of emerging approximate computing applications such multimedia, machine learning and data mining, to drop the refresh rate for the uncritical DRAM regions. By coordinating the potential techniques in circuit, architecture and system level, we aim to propose the techniques of weak cell salvaging, self-adaptive refresh and low-precision refresh, and use them to explore the lower bound of refresh power without compromising the requirement of performance and reliability, and eventually improve the energy-efficiency of modern computing systems.

英文关键词： 3D Stacked;DRAM;TSV;Low Power;DRAM Refresh