Cool chips: Opportunities and implications for power and thermal management

Alongside innovative device, circuit, and microarchitecture level techniques to alleviate power and thermal problems in nanoscale CMOS-based integrated circuits (ICs), chip cooling could be an effective knob for power and thermal management. This paper analyzes IC cooling while focusing on the practical temperature range of operation. Comprehensive analyses of chip cooling for various nanometer scale bulk-CMOS and Silicon-On-Insulator (SOI) technologies are presented. Unlike all previous works, this analysis employs a holistic approach (combines device, circuit and system level considerations) and also takes various electrothermal couplings between power dissipation, operating frequency and die temperature into account. While chip cooling always gives performance gain at the device and circuit level, it is shown that system level power defines a temperature limit beyond which cooling gives diminishing returns and an associated cost that may be prohibitive. A scaling analysis of this temperature limit is also presented. Furthermore, it is shown that on-chip thermal gradients cannot be mitigated by global chip cooling and that localized cooling can be more effective in removing hot-spots.