Thermal coupling analysis and improved dynamic temperature control algorithm for 3D-LSI

3D-LSI techniques are proven to be effective in improving performance without miniaturization of transistors. However, 3D-LSI have problems in heat dissipation, especially in 3D-LSI without TSV. An example is the stacked chips where communication among chips is done wirelessly. It is difficult to dissipate the heat generated by layers not connected to the substrate or the cooler. This is because thermal conduction through TSVs becomes impossible. Therefore, thermal management technology is necessary in the TSV-less 3D stacked chips. In this paper, we investigate the effect of multiple heating sources on each other by simulation. Based on the simulation results, we considered the distance between multiple high heat- sources in the proposed method to further reduce the highest temperature in the chip. In addition, we also designed a task migration algorithm when heat source cross-layer migration is allowed. This improved algorithm can select better task migration targets to reduce the generation of hotspots without changing the overall performance of the chip. Simulation verification was conducted using a commercial thermal analysis software. The results show that our approach can reduce the maximum temperature in the chip by 3-7°C when only intra-layer migration is allowed, and by more than 30°C when cross-layer migration of tasks is allowed.