Thermal modeling, characterization and management of on-chip networks

Due to the wire delay constraints in deep submicron technology and increasing demand for on-chip bandwidth, networks are becoming the pervasive interconnect fabric to connect processing elements on chip. With ever-increasing power density and cooling costs, the thermal impact of on-chip networks needs to be urgently addressed. In this work, we first characterize the thermal profile of the MIT Raw chip. Our study shows networks having comparable thermal impact as the processing elements and contributing significantly to overall chip temperature, thus motivating the need for network thermal management. The characterization is based on an architectural thermal model we developed for on-chip networks that takes into account the thermal correlation between routers across the chip and factors in the thermal contribution of on-chip interconnects. Our thermal model is validated against finite-element based simulators for an actual chip with associated power measurements, with an average error of 5.3%. We next propose ThermalHerd, a distributed, collaborative run-time thermal management scheme for on-chip networks that uses distributed throttling and thermal-correlation based routing to tackle thermal emergencies. Our simulations show ThermalHerd effectively ensuring thermal safety with little performance impact. With Raw as our platform, we further show how our work can be extended to the analysis and management of entire on-chip systems, jointly considering both processors and networks.