Abstract: End-user software is used to select lists of values of control signals from a predetermined design of a processor, and a unique value of an opcode is assigned to each selected list of values of control signals. The assignments, of opcode values to lists of values of control signals, are used to create a new processor design customized for the end-user software, followed by synthesis, place and route, and netlist generation based on the new processor design, followed by configuring an FPGA based on the netlist, followed by execution of the end-user software in customized processor implemented by the FPGA. Different end-user software may be used as input to generate different assignments, of opcode values to lists of control signal values, followed by generation of different netlists. The different netlists may be used at different times, to reconfigure the same FPGA, to execute different end-user software optimally at different times.