The power consumption of digital circuits, e.g., Field Programmable Gate Arrays (FPGAs), is directly related to their operating supply voltages. On the other hand, usually, chip vendors introduce a conservative voltage guardband below the standard nominal level to ensure the correct functionality of the design in worst-case process and environmental scenarios. For instance, this voltage guardband is empirically measured to be 12%, 20%, and 16% of the nominal level in commercial CPUs [1], Graphics Processing Units (GPUs) [2], and Dynamic RAMs (DRAMs) [3], respectively. However, in many real-world applications, this guardband is extremely conservative and eliminating it can result in significant power savings without any overhead. Motivated by these studies, we aim to extend the undevolting technique to commercial FPGAs. Toward this goal, we will practically demonstrate the voltage guardband for a representative Xilinx FPGA, with a preliminary concentration on on-chip memories, or Block RAMs (BRAMs).