What are the benchmarks (MIPS) of an Arduino Uno (ATmega32P) and Arduino Nano 3.0 (Atmega328) @ 1.6MHz?
ATmega16U4/ATmega32U4, ATmega48A/PA/88A/PA/168A/PA/328/P, ATmega2560, and numerous other Atmel AVR 8-Bit microcontrollers have an instruction set typically with “135 Powerful Instructions – Most Single Clock Cycle Execution” per datasheets.
That is, many of the AVR instructions, including almost all of the logic and arithmetic instructions, execute in 1 cycle. A fair number of memory access instructions take 2 cycles. A few instructions (eg JMP) take 3 cycles, and some (RCALL, CALL, RET, RETI, et al) take 4 or 5 cycles. Others (eg SBRC) take 1, 2, or 3 cycles, depending on operand values and whether a branch occurs that disrupts the pipeline, which is shallow. For an overview, see the instruction set summary in any AVR-part datasheet. For details, see Atmel's AVR Instruction Set Manual, doc0856 at atmel.com.
Overall, the average instructions per second in a typical compiled C program probably is between 1.5 and 2, so a 16 MHz system might do 8 to 11 MIPS on average, while carefully tailored do-nothing code can easily achieve 16 MIPS.
Do you mean 16MzHz?
Benchmarks are here.