Optimizing Thermal Performance in 2.5D Systems Using Embedded Isolators

This paper investigates thermal management in tightly integrated heterogeneous chiplet systems, focusing on a novel approach using embedded thermal isolators. In many 2.5D systems, such as modern enterprise GPUs, thermally sensitive chiplets like High Bandwidth Memory (HBM) are thermally coupled to high-power compute chiplets, leading to performance degradation. We propose and evaluate the use of thermal isolators embedded within the heat spreader to effectively thermally decouple chiplets. Our thermal simulations of a water-cooled 2.5D integrated GPU system indicate that conventional approaches like thermally-aware floorplanning are less effective due to the dominant heat transfer through the heat spreader. In contrast, our proposed thermal isolators can significantly increase thermal isolation between chiplets (by up to 61%), or even reduce overall average peak chip temperature (by up to 22.5%). We develop a closed-loop workflow incorporating thermal results to quantify performance impacts of thermal-induced throttling, finding that in an example GPU+HBM system, the isolator approach can yield performance gains of up to 37% for memory-bound workloads. These findings open up new avenues for thermal management and thermal-system co-optimization in 2.5D heterogeneous integrated systems, potentially enabling more efficient and higher-performing chiplet-based architectures.