The energy efficiency of CMP vs. SMT for multimedia workloads

Ruchira Sasanka, Sarita V. Adve, Yen Kuang Chen, Eric Debes

Research output: Contribution to conferencePaperpeer-review


This paper compares the energy efficiency of chip multiprocessing (CMP) and simultaneous multithreading (SMT) on modern out-of-order processors for the increasingly important multimedia applications. Since performance is an important metric for real-time multimedia applications, we compare configurations at equal performance. We perform this comparison for a large number of performance points derived using different processor architectures and frequencies/voltages. We find that for the design space explored, for each workload, at each performance point, CMP is more energy efficient than SMT. The difference is small for two thread systems, but large (18% to 44%) for four thread systems. We also find that the best SMT and the best CMP configuration for a given performance target have different architecture and frequency/voltage. Therefore, their relative energy efficiency depends on a subtle interplay between various factors such as capacitance, voltage, IPC, frequency, and the level of clock gating, as well as workload features. We perform a detailed analysis considering these factors and develop a mathematical model to explain these results. Although CMP shows a clear energy advantage for four-thread (and higher) workloads, it comes at the cost of increased silicon area. We therefore investigate a hybrid solution where a CMP is built out of SMT cores, and find it to be an effective compromise. Finally, we find that we can reduce energy further for CMP with a straightforward application of previously proposed techniques of adaptive architectures and dynamic voltage/frequency scaling. CMP, SMT, Energy Efficiency, Multimedia.

Original languageEnglish (US)
Number of pages11
StatePublished - 2004
Event2004 International Conference on Supercomputing - Saint-Malo, France
Duration: Jun 26 2004Jul 1 2004


Other2004 International Conference on Supercomputing

ASJC Scopus subject areas

  • Computer Science(all)


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