Measurement of Variations in FPGAs under Various Load Conditions

: This paper presents experimental evaluations of operating speed, power consumption, and chip tempera- ture under various load conditions on commercial FPGAs. To measure the operating speed of FPGAs, we count the oscillation frequency of a ring oscillator (RO), which is implemented on one 4-input look-up table (LUT). The load condition on FPGAs can be controlled by the number of activated ROs in parallel around the measurement RO. The measurement results show that operating speed may be decreased more than10% with 142 ROs as load circuits and the degradation rates depend on the measurement location in an FPGA. The evaluation of die-to-die variations using four more FPGA boards show that there exists a non-negligible speed variation.