Many Core Design from a Thermal Perspective: Extended Analysis and Results

Air cooling limits have been a major design challenge in recent years for integrated circuits. Multi-core exacerbates thermal challenges because power scales with the number of cores, but also creates new opportunities for temperature-aware design, because multi-core designs offer more design parameters than single-core designs. This technical report investigates the relationship between core size and on-chip hot spot temperature and shows that with the same power density, smaller cores are cooler than larger cores due to a spatial low-pass filtering effect of temperature. This phenomenon suggests that designs exploiting low-pass filtering can dissipate more power within the same cooling budget than contemporary designs. We also find a decrease of withincore spatial temperature variation for many-core designs,indicating that thermal analysis can be potentially carried out at the core granularity in the future. This report also presents more results in addition to the DAC paper and includes a derivation of the location of the isotherm in the Appendix. Accurately locating the isotherm is required for an accurate temperature model for homogeneous many-core chips.