An Adapative Frequency Control Method using Thermal Feedback for Reconfigurable Hardware Applications

Reconfigurable circuits running in Field Programmable Gate Arrays (FPGAs) can be dynamically optimized for power based on computational requirements and thermal conditions of the environment. In the past, FPGA circuits were typically small and operated at a low frequency. Few users were concerned about high-power consumption and the heat generated by FPGA devices. The current generation of FPGAs, however, use extensive pipelining techniques to achieve high data processing rates and dense layouts that can generate significant amounts of heat. FPGA circuits can be synthesized that can generate more heat than the package can dissipate. For FPGAs that operate in controlled environments, heatsinks and fans can be mounted to the device to extract heat from the device. When FPGA devices do not operate in a controlled environment, however, changes to ambient temperature due to factors such as the failure of a fan or a reconfiguration of bitfile running on the device can drastically change the operating conditions. A protection mechanism is needed to ensure the proper operation of the FPGA circuits when such a change occurs. To address these issues, we have devised a reconfigurable temperature monitoring system that gives feedback to the FPGA circuit using the measured junction temperature of the device. Using this feedback, we designed a novel dual frequency switching system that allows the FPGA circuits to maintain the highest level of performance for a given maximum junction temperature. Our working system has been implemented and deployed on the Field Programmable Port Extender (FPX) platform at Washington University in St. Louis. Our experimental results with a scalable image correlation circuit show up to a 2.4x factor increase in performance as compared to a system without thermal feedback. Our circuit ensures that the device performs the maximum required computation while always operating within a safe temperature range.