Waking up after power failure

[yksyks]

There are several recent threads discussing remote or scheduled PC waking up, but I have seemingly simpler question, which I'm unable to find solution to, though. My problem is: how do I wake a PC (ATX motherboard -- MSI 925X Neo) automatically after power failure? I have an UPS, but if the PC hibernates due to longer outage, is there any simple trick to start the PC unattended? The BIOS doesn't have the "always on" option.

Thanks for any ideas.