I recently bought an old motherboard for 5 bucks, and I'm working on building my first computer. The motherboard comes from an old Dell Dimension 4400, and I'm not sure on the power supply, besides that it is a Dell power supply. The power supply is 24-pin, and the motherboard is 20-pin. Unfortunately, the power supply connector is not one of the new breakaway 20+4-pins. I can still make it fit however by just letting the extra four pins hang off the end. I get a little green LED on the mobo, but no response when I push the power button.
I know the motherboard works because I tested it with the psu from my PC (20-pin), and it worked fine. I researched the wiring for ATX power supplies, and the colors all seem to match up with what I would expect. Is there a good way to test if the power supply is functional or not? I was wondering if it was possible that the psu could somehow sense that the extra four pins were not connected, and would not power up for that reason. Could that be the case?