GreenCool: An Energy-Efficient Liquid Cooling Design Technique for 3-D MPSoCs Via Channel Width Modulation

Abstract

Abstract-Liquid cooling using interlayer microchannels has appeared as a viable and scalable packaging technology for 3-D multiprocessor system-on-chips (MPSoCs). Microchannelbased liquid cooling, however, can substantially increase the onchip thermal gradients, which are undesirable for reliability, performance, and cooling efficiency. In this paper, we present GreenCool, an optimal design methodology for liquid-cooled 3-D MPSoCs. GreenCool simultaneously minimizes the cooling energy for a given system while maintaining thermal gradients and peak temperatures under safe limits. This is accomplished by tuning the heat transfer characteristics of the microchannels using channel width modulation. Channel width modulation is compatible with the current process technologies and incurs minimal additional fabrication costs. Through an extensive set of experiments, we show that channel width modulation is capable of complementing and enhancing the benefits of temperatureaware floorplanning. We also experiment with a 16-core 3-D system with stacked dynamic random-access memory, for which GreenCool improves energy efficiency by up to 53% with respect to no channel modulation.

Power-Thermal Modeling and Control of Energy-Efficient Servers and Datacenters

“…Our recent proposed framework, namely GREENCOOL, optimizes the active cooling path of microchannel-based iterlayer liquid cooled 3D MPSoCs to balance the thermal profile of the target 3D MPSoC while significantly reducing the active cooling energy demands [109]. This design-optimization methodology uses the concept of channel modulation, where we change the microchannel aspect ratio (channel width/channel height) to enhance the heat transfer capability from the target 3D MPSoC via changing the convective thermal resistance [110].…”

“…a With uniform non modulated channel width. b With modulated channel width to compensate for sensible heat absorption [109] where k coolant is the thermal conductivity of the coolant and d h is the hydraulic diameter of channel. The effective heat transfer coefficient as seen by the junction looking down the channel from the top can be written by projecting the heat transfer coefficient above from the side wall surfaces onto the top as follows:…”

“…In another set of experiments to demonstrate the energy-efficiency of GREEN-COOL, significant cooling energy savings that reach up to 80 % has been achieved [109]. Furthermore, GREENCOOL aids in developing efficient cooling layout in the cases where uniform cavity utilization is infeasible.…”

ICCAD 2015 contest in 3D interlayer cooling optimized network

“…There have also been studies to optimize straight channels both at design-time employing methods such as modulating channel-widths [3] or by modifying heat conduction paths by judicious placement of TSVs [4]. There have also been methods proposed to address efficient run-time operation of liquid-cooled microchannels [5].…”

A semi-analytical approach for optimized design of microchannel liquid-cooled ICs

“…We present two state-of-the-art applications of performing robust design optimization using channel width modulation: Application 1 [12] that minimizes on-chip temperature gradients and Application 2 (GreenCool) [13] that minimizes pumping en- …”