[simias]

>e.g. send the processor to a lower-consumption state.

You have to be very careful in a bootloader, since you're initializing the clocks and other very low level subsystems you don't want to risk putting the CPU in a state you won't be able to get out of.

In general the standard method is to use a dummy busy delay like the "nop loop" shown above in the very early stages until you get to the point where you can enable interrupts and standby states and implement a proper sleep method that will effectively shut the CPU down waiting for an external event.

If you're talking about userland code (or even driver code) using busyloops you're right though.