Clock div fuse

[Cside]

Quick ammateur question.
when switching on the clock/div fuse in a micro, what is the effect on power ?

For instance, if we have an 8Mhz external clock and we divide by 8, would the power consumption be comparable to an unfused 1Mhz crystal? I expect it to be somewhere between but I have no dat and little information online. Any experience anyone?

[Artraze]

In terms of the overall system power usage, generally there's not going to be too much difference between using a 1 MHz clock directly and a 8 MHz clock divided by 8.

The power consumed in the crystal is much higher, of course.  It's likely (very) approximately 4 times more, but of course it depends on the specific crystals and oscillator.  It's still not really noticeable in terms of the overall system power during operation... probably only like 2mW.   However, if you put the system into sleep/idle mode and want to keep the oscillator running (so as not to wait for it to startup again) it could be significant.