What makes an ATX server case reboot after a power failure?

[Norssak]

ok, we had a power failure in the server room that drained the UPS and brought everything to a standstill. When the power came back on my Dell servers(ATX..ish) all came back to life on their own. But not all of my homemade boxes (ATX) kicked in automatically.

So the question is, if I want to build boxes that automatically startup after a catastrophic power failure, what do I need to look for? Is it the powersupply or the motherboard which does the trick, and what would be a key-word to look for when selecting components?

Thanxs in advance

 

[BA]

It should be a BIOS setting, whether to stay off, or return to the power state before the outage.

 

[clumsum]

My back-up pc, ............ a Compaq Presario, ...... does the same thing....?
If I'm working on it and have it un-plugged, ....... when I plug it back in ..... it automatically boots up ......!
Can be an inconvenience at times .......?

 

[badguy]

It's the power management funtion of Bios, but you have to adjust the jumpper on some motherboards for example my Supermicro P6DBE.

 

[barlav]

For my mobo (MSI K7T PRO2-A) it was the "State After Power Failure" setting that controlled this.