Multiple PSU rails: How to find out which is which

motherboardpower supply

The title explains it all: I have an Antec VP-450 PSU and it has two 18A 12V rails. There are two yellow wires which I assume are 12V: one is solid yellow and the other has a black stripe. (The yellow go to the CPU connector: that's how I know the 12V is yellow).

  • Am I mistaken or does the stripe indicate different rails?
  • Should I even be worried about rail distribution?
  • It seems to have my motherboard and my GPU on the same rail, is there any way that I could "switch" them? It seems kinda odd to do that.

Best Answer

I would say you should not be worried with the rail distribution on a power supply with only two rails @ 450 watts from a reputable manufacturer like Antec for your CPU and GPU. Video cards and Motherboards use specific connectors that take away your ability to choose what rail the GPU is on and what rail the CPU is on so you have to trust that Antec put them on separate rails or balanced things correctly. Even an un-reputable brand would do this, but maybe there is anomaly out there.

To check for your self, you might be able to take a multimeter to the connectors while the PS is off, disconnected from the motherboard and all other components, and disconnected from the wall. Check the resistance across pins or wires that you know are on a common rail (for example probe between 12V lines on the same connector that have individual leads going to the PS housing) then check the resistance between 12V lines across different connectors; resistance that are approximately the same will be on the same rail and resistances that are different will be on different rails; resistances on separate rails might even have infinite resistance (or "1" on a multimeter)

(NOT RECOMMENDED IF YOU DO NOT KNOW WHAT YOU ARE DOING.) If you want to check by sight, you could crack open the PS case and trace the wires. They should end up on common soldered paths on the boards inside the PS if they are on the same rail, and connectors on separate rails should have leads that have to go through some components in the PS before they combine. But realize the PS has large capacitors that could shock you and possibly kill you (unlikely, but possible!) if you short the capacitors with your body before they are discharged.