Low-latency adaptive mode transitions and hierarchical power management in asymmetric clustered cores

Eran Shifer, Shlomo Weiss*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Recently, engineering solutions that include asymmetric multicores have been fabricated for low form-factor computing devices, indicating a potential direction for future evolution of processors. In this article we propose an asymmetric clustered core architecture, exhibiting low-latency switching between modes relative to asymmetric multicores, and having similarities with the same asymmetric multicore architecture in the context of a wider dynamic range of the processor power-performance characteristic. Asymmetric clustered cores incur additional microarchitectural complexity and area cost inside a core but exhibit better chip-level integration characteristics compared to asymmetric multicores. Focusing on power efficiency of asymmetric clustered cores, we describe: (1) a hierarchical power management partitioning between the operating system and on-die firmware for coarse-grain switch policies, and (2) core-internal tracking hardware for fine-grain switching. The mode switch policies of the core's tracking hardware are dependent on higher-level directives and hints from the operating system, on-die firmware, and compiler or profiling software.We further explore the potential power management benefits of asymmetric clustered cores relative to asymmetric multicores, demonstrating that the ability of asymmetric clustered cores to use tight training periods for adaptive behavior, with low overhead switching between modes, results in a more efficient utilization of power management directives.

Original languageEnglish
Pages (from-to)1-25
Number of pages25
JournalTransactions on Architecture and Code Optimization
Volume10
Issue number3
DOIs
StatePublished - Sep 2013

Keywords

  • Architecture
  • Asymmetric multicores
  • Clustered cores
  • Core morphing
  • Energy delay
  • Heterogeneous systems
  • Power

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