Abstract: A conventional instruction set architecture such, as the x86 instruction set architecture, may be reencoded to reduce the amount of memory used by the instructions. This may be particularly useful in applications that are memory sized limited, as is the case with microcontrollers. With a reencoded instruction set that is more dense, more functions can be implemented or a smaller memory size may be used. The encoded instructions are then naturally decoded at run time in the predecoder and decoder of the core pipeline.