Check the service processor setup.
There is an option for unattended boot in power section.

"Joao" <jb@dpi.inpe.br> wrote in message
news:bfr59a$4k7$1@server.ltid.inpe.br...
> Our IBM RISC System/6000 E30 does not boot after
> a power fault. It is necessary to press the power
> switch to boot it.
>
> Is it possible to change its behavior,
> so it automatically boot when the power returns?
>
> Thanks,
>
> Joao
>