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.
  • How exactly did you determine your GPU and CPU were on the same rail? If your GPU requires additional power it has its own rail. – Ramhound Feb 12 '14 at 23:34
  • @Ramhound I think that because one has a solid yellow wire and the other is yellow with a black stripe. I just assumed that those two would be different. I checked both. It's just an assumption but I don't know how I should handle this. – Anonymous Penguin Feb 13 '14 at 1:44
  • +1 I like this question though i'd note that this question is probably ok here but would've been better in electronics.stackexchange in that you may have got more technical answers or more explanation, though perhaps too technical there. just worth bearing in mind. – barlop Feb 13 '14 at 8:20
  • @barlop I guess EE.SE might of been good too but this seemed more likley to catch a user who knew the answer. – Anonymous Penguin Feb 13 '14 at 13:51
  • out of interest, how many yellow wires are striped and how many not striped? seriously 2? so you shouldn't have many doubts here! BTW If two yellow wires are on a dual rail then they ARE the same rail! – barlop Feb 13 '14 at 20:58
up vote 1 down vote accepted

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.

  • Could you clarify and explain how you would test the resistance across a rail? The multimeter has 2 probes, call them red and black. Does he A)put the red one on the metal of the pin he wants to test, and the black one to something big and metal? or does he B)put one probe on a pin he wants to test and the other probe on the other pin he wants to test? So, which is it, A or B? And should he and can he do this with PSU off/no power to it? – barlop Feb 13 '14 at 8:19
  • Tried editing the answer to give more information. The way is B, probe on a pin he wants to test and the other probe on the other pin he wants to test. Feel free to edit it if it can be made clearer! – Damon Feb 13 '14 at 8:43
  • What can go wrong if testing it with PSU on and plugged in? No doubt there's no danger to a human because it's low current and low voltage DC. Would it A)give the wrong result or B)damage the MBRD or a component? (A? B? neither? both?) – barlop Feb 13 '14 at 15:10
  • @barlop I could assume some answers, but I really cannot give exact answers to those question. I am guessing the caveats/risks you mention are all valid, plus ones you haven't mentioned. One could research how to properly test the resistance of a circuit to see what would be safe and accurate to do. – Damon Feb 13 '14 at 15:52
  • ok, though bear in mind then that some of your precautions may just be time wasting and scare mongering. though it can make sense to take such precautions if in doubt. It's a reasonable answer for superuser – barlop Feb 13 '14 at 19:49

Here is the power supply that you have. Antec VP450

enter image description here

`Features

• 450 watts of Continuous Power • ATX12V version 2.3 compliant
Dual +12V rails ensure greater system stability ...........

The spec says "DUAL 12V rails"

If as you suggest, the power supply has just Two yellow(12V) wires, then it should be blatantly obvious that they are "colour coded" differently to show you they belong to the same rail, they're part of the dual rail. And even if they were not "colour coded". If they were only two(as you suggest) then obviously those are the two mentioned in the Specification, which says 12V dual rail!

This tomshardware forum link mentions something on it, but this post on overclockers forum is far more comprehensive.

To quote from it

What is "multiple +12V rails", really?

In most cases, multiple +12V rails are actually just a single +12V source just split up into multiple +12V outputs each with a limited output capability.

And

Ok... What's the bottom line?

The bottom line is, for 99% of the folks out there single vs. multiple +12V rails is a NON ISSUE. It's something that has been hyped up by marketing folks on BOTH SIDES of the fence. Too often we see mis-prioritized requests for PSU advice: Asking "what single +12V rail PSU should I get" when the person isn't even running SLI! Unless you're running a plethora of Peltiers in your machine, it should be a non-issue assuming that the PSU has all of the connectors your machine requires and there are no need for "splitters" (see Example 1 in the previous bullet point).

That might not answer everything but it answers a bit.

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