Write energy reduction for PCM via pumping efficiency improvement

Huizhang Luo, Qing Liu, Jingtong Hu, Qiao Li, Liang Shi, Qingfeng Zhuge, Edwin H.M. Sha

Research output: Contribution to journalArticlepeer-review

Abstract

The emerging Phase Change Memory (PCM) is considered to be a promising candidate to replace DRAM as the next generation main memory due to its higher scalability and lower leakage power. However, the high write power consumption has become a major challenge in adopting PCM as main memory. In addition to the fact that writing to PCM cells requires high write current and voltage, current loss in the charge pumps also contributes a large percentage of high power consumption. The pumping eficiency of a PCM chip is a concave function of the write current. Leveraging the characteristics of the concave function, the overall pumping eficiency can be improved if the write current is uniform. In this article, we propose a peak-to-average (PTA) write scheme, which smooths the write current fluctuation by regrouping write units. In particular, we calculate the current requirements for each write unit by their values when they are evicted from the last level cache (LLC). When the write units are waiting in the memory controller, we regroup the write units by LLC-assisted PTA to reach the current-uniform goal. Experimental results show that LLC-assisted PTA achieved 13.4% of overall energy saving compared to the baseline.

Original languageEnglish (US)
Article number27
JournalACM Transactions on Storage
Volume14
Issue number3
DOIs
StatePublished - Nov 2018

All Science Journal Classification (ASJC) codes

  • Hardware and Architecture

Keywords

  • Charge pump
  • Phase change memory (PCM)
  • Pumping eficiency
  • Write regrouping

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