While searching for a way to take logs on an FPGA (without resorting to the sledgehammer of CORDIC) I stumbled upon Micheal Dunn’s Single-cycle logarithms & antilogs article in EDN. His method is a clever extention of the mathematician’s approximation: to take the log (base 10), just count the digits. In binary we can get the log (base 2) by “counting the digits” with a priority encoder—which outputs the position of the highest nonzero bit.