TuneFPGA: Post-silicon tuning of dual-Vdd FPGAs

Modern CMOS manufacturing processes have significant variability, which necessitates guard banding to achieve reasonable yield. We study an FPGA architecture with a dual voltage supply wherein the supply voltage for individual CLBs can be assigned after fabrication; this yields a mechanism for fixing chips that fail because of manufactured transistors being slower than designed. The fundamental advance our work makes is that we assign voltages based on manufactured data rather than designed values. The key contributions of our work are a CAD methodology and a detailed quantitative study using realistic data on the latest process technologies of the impact of post-manufacturing tuning on yield and power for dual-Vdd FPGAs. We find that, for a representative modern process, post-manufacturing tuning can increase the yield by up to 10 x compared with a conventional dual-Vdd design that selects the voltage supply pre-manufacturing, even with guard banding. Overall, the geometric mean of yield/power ratio is 27% greater using post- manufacturing tuning.