Power down from software

By compiling in APM to the kernel

If you have a modern ATX motherboard with APM power support compiled in, then "halt" will powerdown the system.

The Kernel compile options for APM under 2,2,x are found in "General Setup" "Advanced Power Management BIOS support".

After you have rebooted into the new kernel or loaded the modules, then the halt command or shutdown now -h will result in the machine turning itself off.