Optimizing Leakage Energy Consumption in Cache Bitlines

As technology scales down into deep-submicron, leakage energy is becoming a dominant source of energy consumption. Leakage energy is generally proportional to the area of a circuit and caches constitute a large portion of the die area. Therefore, there has been much effort to reduce leakage energy in caches. Most techniques have been targeted at cell leakage energy optimization. Bitline leakage energy is critical as well. To this end, we propose a predictive precharging scheme to reduce bitline leakage energy consumption. Results show that energy savings are significant with little performance degradation. Also, our predictive precharging is more beneficial in more aggressively scaled technologies.     

A Case for Asymmetric-Cell Cache Memories

In this paper, we make the case for building high-performance asymmetric-cell caches (ACCs) that employ recently-proposed asymmetric SRAMs to reduce leakage proportionally to the number of resident zero bits. Because ACCs target memory value content (independent of cell activity and access patterns), they complement prior proposals for reducing cache leakage that target memory access characteristics. Through detailed simulation and leakage estimation using a commercial 0.13-$mu$m CMOS process model, we show that: 1) on average 75% of resident data cache bits and 64% of resident instruction cache bits are zero; 2) while prior research carefully evaluated the fraction of accessed zero bytes, we show that a high fraction of accessed zero bytes is neither a necessary nor a sufficient condition for a high fraction of resident zero bits; 3) the zero-bit program behavior persists even when we restrict our attention to live data, thereby complementing prior leakage-saving techniques that target inactive cells; and 4) ACCs can reduce leakage on the average by 4.3$times$compared to a conventional data cache without any performance loss, and by 9$times$at the cost of a 5% increase in overall cache access latency.     

纳米级CMOS电路的漏电流及其降低技术

随着CMOS工艺的进一步发展,漏电流在深亚微米CMOS电路的功耗中变得越来越重要.因此,分析和建模漏电流的各种不同组成部分对降低漏电流功耗非常重要,特别是在低功耗应用中.本文分析了纳米级CMOS电路的各种漏电流组成机制并提出了相应的降低技术.     

适于深亚微米器件模拟的Monte Carlo方法

讨论了用于深亚微米半导体器件模拟的Ｍｏｎｔｅ Ｃａｒｌｏ 方法（ＭＣＭ）,探讨了确定自由飞行时间的自散射方法,并简要阐述了玻耳兹曼模型（ＢＴＭ）、漂移扩散模型（ＤＤＭ）和流体动力学模型（ＨＤＭ）之间的关系。     

Enhanced Leakage Reduction Techniques Using Intermediate Strength Power Gating

The exponential increase in leakage power due to technology scaling has made power gating an attractive design choice for low-power applications. In this paper, we explore this design style in large combinational circuit blocks and latch-to-latch datapaths and introduce a novel power gating approach to yield an improved power-performance tradeoff. We first present a multiple sleep mode power gating technique where each mode represents a different point in the wake-up overhead versus leakage savings design space. We show that the high wake-up latency and wake-up power penalty of traditional power gating limits its application to large stretches of inactivity. The multiple-mode feature allows a processor to enter power saving modes more frequently, hence, resulting in enhanced leakage savings. We apply the multimode power gating technique to datapaths where the degree of applied power gating becomes progressively stronger (harder) along the datapath. This configuration allows us to further balance wake-up overhead with leakage savings by exploiting the fact that logic circuits deep in the datapath have higher wakeup margin and hence can be strongly gated. Simulations show that multiple sleep mode capability provides an extra 17% reduction in overall leakage compared to traditional single mode gating. The multiple modes can be designed to allow state-retentive modes. The results on benchmarks show that a single state-retentive mode can reduce leakage by 19% while preserving state of the circuit.     

现代微处理器的Cache设计技术

本文对现代微处理器Ｃａｃｈｅ设计的关键要素，包括Ｃａｃｈｅ的相联度、寻址方式、透明性实现、失配处理方式、结构与层次等，进行了详细的讨论；对每一要索的各种可能选择进行了分析与比较，并讨论了这些要素在各类最新微处理器Ｃａｃｈｅ设计中的实现。     

Leakage Current Reduction Techniques for 7T SRAM Cell in 45 nm Technology

In this paper the impact of gate leakage on 7T static random access memory (SRAM) is described and three techniques for reducing gate leakage currents and sub threshold leakage currents are examined. In first technique, the supply voltage is decreased. In the second techniques the voltage of the ground node is increased. While in third technique the effective voltage across SRAM cell Vd = 0.348V and Vs = 0.234V are observed. In all the techniques the effective voltage across SRAM cell is decreased in stand-by mode using a dynamic self controllable voltage level (SVL) switch. Simulation results based on cadence tool for 45 nm technology show that the techniques in which supply voltage level is reduced is more efficient in reducing gate leakage than the one in which ground node voltage is increased. Result obtained show that 437 FA reductions in the leakage currents of 7T SRAM can be achieved.     

面向访问需求的数据缓存泄漏功耗管理方法

 本文提出面向访问需求的数据缓存泄漏功耗管理方法,根据访存指令对数据缓存的访问需求控制数据缓存的活动.当流水线中未发现访存指令时,将整个数据缓存保持在非活跃状态;而当发现访存指令进入流水线时,采用两种数据缓存访问控制策略以及对这两种策略的动态选择机制,在流水线早期捕获访存地址的访问需求,对数据缓存的活动作出精细控制.实验结果表明,在平均情况下,本文方法将数据缓存的泄漏功耗降低85.4%,而处理器性能提升4.41%,比传统方法在功耗与性能方面均达到更优结果.     

Code and Data Placement for Embedded Processors with Scratchpad and Cache Memories

This paper proposes a code placement problem, its ILP formulation, and a heuristic algorithm for reducing the total energy consumption of embedded processor systems including a CPU core, on-chip and off-chip memories. Our approach exploits a non-cacheable memory region for an effective use of a cache memory and as a result, reduces the number of off-chip accesses. Our algorithm simultaneously finds a code layout for a cacheable region, a scratchpad region, and the other non-cacheable region of the address space so as to minimize the total energy consumption of the processor system. Experiments using a commercial embedded processor and an off-chip SDRAM demonstrate that our algorithm reduces the energy consumption of the processor system by 23% without any performance degradation compared to the best result achieved by the conventional approach.     

LRU-Assist:一种高效的Cache漏流功耗控制算法

随着集成电路制造工艺进入超深亚微米阶段,漏电流功耗在微处理器总功耗中所占的比例越来越大,在开发新的低漏流工艺和电路技术之外,如何在体系结构级控制和优化漏流功耗成为业界研究的热点.Cache在微处理器中面积最大,是进行漏流控制的首要部件.LRU是组相联Cache最常用的替换算法,而研究发现,访存操作命中LRU后半区的概率很低.LRU-Assist算法以Drowsy Cache、Cache Decay等控制策略为基础,在保证处理器性能不受影响的前提下,利用既有的LRU信息把Cache的关闭率平均提高了15％,大大降低了漏电流功耗.     

Proposed Design of 1 KB Memory Array Structure for Cache Memories

Wireless Personal Communications - Technology scaling facilitates to meet ever increasing demands for a portable and battery operated systems, at the same time causes diminution of length of the...     

MOSFET衬底电流模型在深亚微米尺寸下的修正

建立精确的衬底电流模型是分析ＭＯＳＦＥＴ器件及电路可靠性和进行ＭＯＳＦＥＴ电路设计所必需的．在分析载流子输运的基础上建立了一个常规结构深亚微米ＭＯＳＦＥＴ衬底电流的解析模型,模型公式简单．对模型进行了验证,研究了衬底掺杂浓度与栅氧化层厚度对拟合因子的影响,并分析了模型中拟合因子的物理意义．     

MOSFET衬底电流模型在深亚微米尺寸下的修正

建立精确的衬底电流模型是分析MOSFET器件及电路可靠性和进行MOSFET电路设计所必需的.在分析载流子输运的基础上建立了一个常规结构深亚微米MOSFET衬底电流的解析模型,模型公式简单.对模型进行了验证,研究了衬底掺杂浓度与栅氧化层厚度对拟合因子的影响,并分析了模型中拟合因子的物理意义.     

基站节能减排技术浅析

简要阐述了通信行业节能减排市场发展需求,较详细介绍分析了移动通信基站功放节能技术,智能载波调节、基带板智能下电、ATCA平台架构、多载波动态功率共享等产品节能技术,以及绿色包装、资源利旧、机房智能温控系统、机房动力方案等网络综合节能技术。     

静态随机存取存储器漏电流功耗降低技术

分析了静态随机存取存储器 (SRAM) 的漏电流,总结了目前业界所用的各种降低漏电流的技术,包括衬底偏压、源极偏压、双电源电压、字线电压反偏和位线电压浮动结构.它们都是通过改变SRAM各个端点的电压来实现的,在降低漏电流的同时,对SRAM器件性能也有一定的影响.基于UMC 55 nm CMOS工艺,对几种方案进行了仿真,并在理论分析的基础上,指出未来发展的趋势.     

静态随机存储器低泄漏设计技术

随着CMOS工艺发展,高性能SoC的泄漏功耗占整体能耗的比例越来越大,内嵌存储器的泄漏是整体泄漏的主要来源,有两方面原因:(1)芯片内嵌的静态随机存储器SRAM容量越来越大;(2)每次访存操作时SRAM仅小部分阵列工作,大部分存储阵列处于非工作状态.总结SRAM低泄漏的电路设计技术,并总结工艺发展对于低泄漏设计技术的挑...     

Efficient BISR Techniques for Embedded Memories Considering Cluster Faults

Instead of the traditional spare row/column redundancy architectures, block-based redundancy architectures are proposed in this paper. The redundant rows/columns are divided into row/column blocks. Therefore, the repair of faulty memory cells can be performed at the row/column-block level. Moreover, the redundant row/column blocks can be used to replace faulty cells anywhere in the memory array. This global characteristic is helpful for repairing cluster faults. The proposed redundancy architecture can be easily integrated with the embedded memory cores. Based on the proposed global redundancy architecture, a heuristic modified essential spare pivoting (MESP) algorithm suitable for built-in implementation is also proposed. According to experimental results, the area overhead for implementing the MESP algorithm is very low. Due to efficient usage of redundancy, the manufacturing yield, repair rate, and reliability can be improved significantly.      

Fine-Grain Sleep Transistor Insertion for Leakage Reduction

首先给出一种泄漏电流和延时的简化模型,并且在此基础上提出了一种降低泄漏电流的细粒度休眠晶体管插入法.该方法的核心是利用混合整数线性规划方法同时确定插入细粒度休眠晶体管的位置和尺寸.从实验结果可以发现,由于这种方法更好地利用了电路中的延时余量,所以在电路性能不受影响的情况下可以减小79.75%的泄漏电流;并且在一定范围内放宽电路的延时约束可以更大幅度地降低泄漏电流.与传统的固定放宽延时约束的方法相比较,当延时约束放宽7%时,这种方法可以节约74.79%的面积.     

降低泄漏电流的细粒度休眠晶体管插入法

首先给出一种泄漏电流和延时的简化模型,并且在此基础上提出了一种降低泄漏电流的细粒度休眠晶体管插入法.该方法的核心是利用混合整数线性规划方法同时确定插入细粒度休眠晶体管的位置和尺寸.从实验结果可以发现,由于这种方法更好地利用了电路中的延时余量,所以在电路性能不受影响的情况下可以减小79.75%的泄漏电流;并且在一定范围内放宽电路的延时约束可以更大幅度地降低泄漏电流.与传统的固定放宽延时约束的方法相比较,当延时约束放宽7%时,这种方法可以节约74.79%的面积.     

并行文件系统PARFSNOW++中的CooperativeCache技术的研究

本文介绍了并行文件系统PARFSNOW++中采用的有权限控制的复合协作式缓冲管理机制,并针对当前协作式缓冲机制中的问题,提出了新的全局内存数据同步和数据替换策略.它们能有效地提高全局内存数据同步和缓冲数据替换的效率.通过实验,本文证明了引入这种改进的协作式缓冲机制后,并行文件系统效率得到了提高.