Reducing pipeline energy demands with local DVS and dynamic retiming
Reducing pipeline energy demands with local DVS and dynamic retiming
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通过本地 DVS 和动态重定时降低管道能源需求
DOI：
10.1145/1013235.1013313
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
T. Mudge
中科院分区：
文献类型：
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作者：
Seokwoo Lee;Shidhartha Das;Toan Pham;T. Austin;D. Blaauw;T. Mudge
电压和能量之间的二次关系使动态电压缩放（DVS）成为减少系统功率需求的最强大技术之一。最近，通过消除插入传统设计中的昂贵的电压利润来确保始终校正的操作，诸如剃须刀DVS，电压过度和智能能源管理等技术已经出现了，以进一步降低电压。全球电压控制器可以剃光电压距离的程度受管道阶段潜伏期失衡的限制。由于所有管道阶段都具有相同的电压，因此行使最长关键路径的阶段将定义系统的总体电压，即使其他阶段可能在较低的电压下运行。在本文中，我们在Razor DVS的背景下评估了两种本地调整机制，DVS是一种局部电压控制器方案，允许每个管道阶段其自身的电压水平，以及一个较低的成本动态重新段计划，该方案结合了每个阶段时钟延迟元素以允许更长的时间 - 延迟管道阶段到较短的延迟阶段“借用”时间。使用模拟，我们从研究中得出了两个关键见解。首先，减轻管道阶段不平衡会促进额外的DVS节能。具有动态回开始的剃须管设计在全球电压控制上额外节省了12％的能源（与完全固定的DVS相比，总体节能超过28％）。其次，我们证明了不平衡不仅来自设计因素，而且还来自运行时特征。随着程序（或程序阶段）的变化，我们会在经常行使多个阶段中看到不同的逻辑路径，因此需要对本地控制进行动态微调。该结果表明，即使是均衡的管道也可以受益于动态重测。
The quadratic relationship between voltage and energy has made dynamic voltage scaling (DVS) one of the most powerful techniques to reduce system power demands. Recently, techniques such as Razor DVS, voltage overscaling, and intelligent energy management have emerged as approaches to further reduce voltage by eliminating costly voltage margins inserted into traditional designs to ensure always-correct operation. The degree to which a global voltage controller can shave voltage margins is limited by imbalances in pipeline stage latency. Since all pipeline stages share the same voltage, the stage exercising the longest critical path will define the overall voltage of the system, even if other stages could potentially run at lower voltages. In this paper, we evaluate two local tuning mechanisms in the context of Razor DVS, a local voltage controller scheme that allows each pipeline stage its own voltage level, and a lower cost dynamic retiming scheme that incorporates per-stage clock delay elements to allow longer-latency pipeline stages to "borrow" time from shorter-latency stages. Using simulation, we draw two key insights from our study. First, mitigating pipeline stage imbalances render additional DVS energy savings. A Razor pipeline design with dynamic retiming finds an additional 12% energy savings over global voltage control (resulting in overall energy savings of more than 28% compared to fully-margined DVS). Second, we demonstrate that imbalances arise not only from design factors, but also from run-time characteristics. As the program (or program phase) changes, we see different logic paths in multiple stages exercised frequently, necessitating a dynamic fine-tuning of local control. This result suggests that even well-balanced pipelines could benefit from dynamic retiming.