Power Question (a bit OT)

[Tom Spec <samag70-ignore yahoo ca>]

Can anyone tell me what it is within a machine that gets it to boot up again after it has lost power?  
  
  I have some machines where, if we have a power outage it will crash,  but then immediately boot up once power is restored.  I have  others that crash and need to be manually powered on when the power is  restored.  Is there a name for this feature?  Is there a way  for me to tell how a machine will behave in this regard without  actually yanking the power to find out?
  
  Thanks,
  Tom