On an ATmega328P (8-bit AVR microcontroller), using uint8_t instead of unsigned int for ISR counter variables significantly reduces instruction and cycle count. AVR-GCC defaults to 16-bit integers, so 16-bit arithmetic on an 8-bit MCU requires extra load/store and multi-cycle instructions like adiw. The uint8_t version cuts the ISR code roughly in half. Trade-offs include reduced counter capacity (0xff vs 0xffff) and portability concerns — the optimization is architecture-specific. Solutions include a conditional typedef or the standard uint_fast8_t type, which resolves to the fastest integer width for the target architecture.
