I tried to set my fuses such that the chip runs at 128kHz. The objective is literally to get it to run at 128kHz.
The bigger goal is a battery powered device, but I read that it's probably more power efficient to run at a high clock freq. and get back to sleep faster, so I'm aware that it probably doesn't make sense to run at 128kHz, but I just want to understand what's going on. It will simply flash a LED for halve a sec, then sleep for three sec. That's it for now.
The problem is that a _delay_ms(5000); is in reality much shorter than five seconds, more like halve a second. In fact I have to #define F_CPU to about 1MHz to make it approx. five seconds: an order of magnitude bigger than expected. It looks like my chip is not actually running at 128kHz, even though I think I configured the fuses to do so.
My fuses: -U lfuse:w:0x7b:m -U hfuse:w:0xff:m (used engbedded fuse calc. with CKDIV8 unchecked).
any thoughts? PS: makefile and main.c attached.