Mosaic: Exploiting the spatial locality of process variation to reduce refresh energy in on-chip eDRAM modules

Aditya Agrawal, Amin Ansari, Josep Torrellas

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

EDRAM cells require periodic refresh, which ends up consuming substantial energy for large last-level caches. In practice, it is well known that different eDRAM cells can exhibit very different charge-retention properties. Unfortunately, current systems pessimistically assume worst-case retention times, and end up refreshing all the cells at a conservatively-high rate. In this paper, we propose an alternative approach. We use known facts about the factors that determine the retention properties of cells to build a new model of eDRAM retention times. The model is called Mosaic. The model shows that the retention times of cells in large eDRAM modules exhibit spatial correlation. Therefore, we logically divide the eDRAM module into regions or tiles, profile the retention properties of each tile, and program their refresh requirements in small counters in the cache controller. With this architecture, also called Mosaic, we refresh each tile at a different rate. The result is a 20x reduction in the number of refreshes in large eDRAM modules - practically eliminating refresh as a source of energy consumption.

Original languageEnglish (US)
Title of host publication20th IEEE International Symposium on High Performance Computer Architecture, HPCA 2014
PublisherIEEE Computer Society
Pages84-95
Number of pages12
ISBN (Print)9781479930975
DOIs
StatePublished - 2014
Event20th IEEE International Symposium on High Performance Computer Architecture, HPCA 2014 - Orlando, FL, United States
Duration: Feb 15 2014Feb 19 2014

Publication series

NameProceedings - International Symposium on High-Performance Computer Architecture
ISSN (Print)1530-0897

Other

Other20th IEEE International Symposium on High Performance Computer Architecture, HPCA 2014
Country/TerritoryUnited States
CityOrlando, FL
Period2/15/142/19/14

ASJC Scopus subject areas

  • Hardware and Architecture

Fingerprint

Dive into the research topics of 'Mosaic: Exploiting the spatial locality of process variation to reduce refresh energy in on-chip eDRAM modules'. Together they form a unique fingerprint.

Cite this