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Is it possible (and safe/reliable/non-damaging) to use a 20-pin ATX PSU with a 24-pin ATX motherboard?

So the power supply (I hope) went on one of my computers during an electrical storm recently, and the computer won't start. I have an old PSU, but unfortunately it only has a 20 pin connector, and my motherboard has a 24 pin header. I don't need the system to run, I just need it to POST. After I determine that it isn't the motherboard that has died, I can pick up an adapter. What I need to know is will it even get that far without the adapter? I'd rather not pull a PSU from one of my other computers just for testing.


Yes it is possible, but not recommended. It is better to buy a 20 to 24-pin adapter to avoid power problems with PCI-e cards that do not have their own power connector. See below diagram, make sure it's all the way to the right:

enter image description here

  • 1
    Fortunately, the good folks behind the ATX standard actually keyed the connectors so it would be impossible to plug the 20-pin into the 24-pin the wrong way.
    – crasic
    Aug 11 '11 at 0:59
  • Yes, I will be buying an adapter in the coming days. As far as PCIe goes, all I have in there is a nVidia 7600GT (or GS, I forget). Nothing too power hungry.
    – MBraedley
    Aug 11 '11 at 2:00

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