The megaAVR and AVR Dx families are based on the well-recognized AVR CPU, but the AVR Dx benefits from an updated version of the classic core. The megaAVR instruction set is fully supported by the AVR Dx core, and the execution time is improved. The differences are handled by a C/C++ compiler, but the users that are porting time-critical or cycle-accurate code must refer to the AVR® Instruction Set Manual to verify that the execution time is within the accepted range.