An example design structure tangibly embodied in a machine readable medium includes a first arithmetic logic unit (ALU) to perform fixed point instructions using at least two general registers to read data from a first and second general register of a plurality of general registers and write a result in at least a third general register of the plurality of general registers. The design structure includes a second ALU to perform non-updating fixed point instructions using at least two general registers to only read data from the general registers. The design structure includes an efficiency logic unit coupled to the first ALU and the second ALU. The efficiency logic unit is to receive an instruction and determine whether the received instruction is an updating fixed point instruction or a non-updating fixed point instruction based on a number of general registers to be used to execute the received instruction.