Hi,

I know it is possible to set some Open Firmware variable that makes the machine auto-start when the power is restored after forced shut down (OSX does that through 'Energy Saver' settings, you just have to turn the 'Start up automatically after a power failure' switch on).

Now - does anybody know if there's another way to do this (for example - a simple command in Open Firmware, with no need to boot to OSX)?

\ Go to device node
dev via-pmu

\ Clear previous settings
pad 2 ff fill pad 2 " "(00 FF FF)" 8f pmu-op pad swap dump

\ Now set the acwakeoninsert byte.
pad 2 ff fill pad 2 " "(01 00 02)" 8f pmu-op pad swap dump

ref

@polluks

Do note that this is hardware-specific and won't work on all PowerMacs.