Hello, I just purcached an antec bp550 plus 550w atx12v v2.3 modular power supply. I got it cause i wanted easy cable management but i have no clue what the red modular plug is for. i doubt its for the power to the motherboard. it also has a P3 +P3 which i assume is 8-pin (4+4) ATX12V connector. I plugged in everything and its ready to go but i got no power going to the motherboard. idk what i did wrong. Maybe its the motherboard, it could be dead. i tried the Paper clip test and the PSU fan is spinning so its not the motherboard.
So my question is if the red peice means anything important. that should be connected. i just figured it was for the PCI Express.