Nah, some MCUs have low power modes.
ESP32 has 5 of them, from disabling fancy features, throttling the clock, even delegating to an ultra low power coprocessor, or just going to sleep until a pin wakes it up again. It can go from 240mA to 150uA and still process things, or sleep for only 5uA.
This should be the new isEven()/isOdd(). Calculate the speed of the CPU and use that to determine how long it might take to achieve a ‘sleep’ of a required time.
I took an embedded hardware class where specifically we were required to manually calculate our sleeps or use interrupts and timers rather than using a library function to do it for us.
This was in 1985, on a ABC80, a Swedish computer with a 3 MHz CPU. So, in theory it would be much faster, but I assume there were many performance losses (slow basic interpretor and thing like that) so that for loop got close enough to a second for us to use.
