Voltage margins identification on commercial x86-64 multicore microprocessors

In this paper, we explore the pessimistic voltage guardbands of two multicore x86-64 microprocessor chips that belong to different microarchitectures (one ultra-low power and one high-performance microprocessor), when programs are executed on individual cores of the CPU chips. We also examine the energy and temperature gains as positive effects of lowering the voltage in both chips while preserving the functional correctness of programs. The behavior of the cores was examined executing 8 different workloads from the SPEC CPU2006 suite. Our differential experimental study is performed on two state-of-the-art x86-64 microprocessors: an ultra-low power Intel Core i5-4200U and a high-performance Intel Core i7-3970X. Based on the results, the cores on each microprocessor chip behave differently for different workloads when undervolted, and the voltage guardbands are more than 15% below the nominal voltage levels. We show that the energy efficiency can be increased by a maximum of 20% and the reduction of temperature can be up to 25%.

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