Any harm in applying 12V/5V/3.3V rails "early"?

Discussion in 'Power Supplies' started by Spoonerd, Dec 1, 2013.

  1. Spoonerd

    Spoonerd n00b

    Jan 3, 2013
    Was thinking of sharing a large efficient 12V power supply to power multiple boxes. Think there is any harm on sending the 12V to the mobo (ATX and EPS plug) and GPUs before PWR_ON is signaled from the motherboard? May also consider doing 5V and 3.3V too.

    I would expect this wouldn't be a problem because those 12V rails probably go to a regulator which simply isn't enabled until PWR_ON. I think I would want to make sure +5stby is present before sending the 12V though to make sure any pull-up/down on a regulator enable pin is where it should be.

    I might see how 5V and 3.3V go directly to a USB power switch or card slot so I'm a little more hesitant on those.
  2. Firebug24k

    Firebug24k [H]Lite

    Aug 31, 2006
    It's working for me, I've got a dual P/S setup where I power up the 12V supply first, no issues so far.