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Mobo has 4-pin 12V connector, but PSU has 8-pin. What Can I do?

Last response: in Motherboards
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July 17, 2011 2:52:57 AM

Hey Everyone, (Wasn't sure if this belonged in PSU or Mobo so please move if it's in the wrong place)

Building a computer for a friend. So I have this mobo

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

and this PSU

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

As you can see, the mobo has a 4-pin 12V rail but the PSU only has an 8-pin.

I was able to kind of get 4 of the pins from the 8-pin to fit, but there's a (capacitor I think?) right next to the 4-pin connector on the mobo that prevents me from pushing it down into place.

Would buying some kind of 8-pin to 4-pin adapter be alright or is this unsafe? I really hope I don't have to return anything, just bought all the parts and installed it so (well most of it, just need to plug everything). Thanks for the help!!!
a c 435 V Motherboard
July 17, 2011 2:59:09 AM

The connector only fits one way. If you read the manual, it should tell you which 4 pins to use; most brand new boards have the second 4 pins covered with tape so you know which ones to use with the old 4 pin connector. I only use 4 pins of the 8 pins, and my cpu and ps work fine.
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July 17, 2011 3:05:50 AM

Yea I went through the manual for PSU and mobo multiple times and didn't see any info on it.

But when inserting it I was able to get the left 4-pins on the 8-pin connector to fit. However, the right 4-pins were hanging off the side, and when I pushed it down to try to get it to click in, the right 4 hanging pins would hit some part (I'm not sure what it is) on the motherboard.

Here's a pic, I've circled the part it hits in red

http://i56.tinypic.com/zujx1g.jpg

So as you can see, I can't get it in all the way. Any advice would be much appreciated, Thanks!
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a b V Motherboard
July 17, 2011 3:49:20 AM

Exchange the power supply. Many power supplies have a connector that splits so you can use it as 8 or 4 pins. Many of the modular supplies come with both 8 pin and 4 pin cables.

Breaking the connector to use just half is an option, but it seems like a last resort. I think you know which half you want :) 

If there were an 8 to 4 adapter, it would be safe.

You are perfectly OK using just 4 of the 8 pins - they usually connect to the same rails in the power supply - the only reason for having multiple pins/wires is to spread the current across more wiring. If the motherboard only has a 4 pin connector, then it will only draw as much current as those 4 pins can carry safely.
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a b V Motherboard
July 17, 2011 3:50:32 AM

o1die said:
The connector only fits one way. If you read the manual, it should tell you which 4 pins to use; most brand new boards have the second 4 pins covered with tape so you know which ones to use with the old 4 pin connector. I only use 4 pins of the 8 pins, and my cpu and ps work fine.


I think you misunderstood. The OP is saying that the motherboard has 4 pins, and the power supply has 8, not the other way around.
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a c 435 V Motherboard
July 17, 2011 10:26:37 AM

You are correct. So breaking the 8 pin into two sections isn't an option? Then his ps should have a separate 4 pin. My bad.
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a c 156 V Motherboard
July 17, 2011 12:10:31 PM

The Corsair PSU's do not have an 8 pin CPU power connector. They have a "4+4" connector that can be split. Separate the two halves and tie one back out of the way.

That red circled part that the 8 pin connector touches is an electrolytic capacitor. The metal case is at ground potential. If the wrong part of the connector touches it, you could short 12 volts directly to ground. Undesirable. :) 

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July 17, 2011 1:49:51 PM

Thanks! Yea I went back over there last night thinking I'd have to swap the PSU or get an adapter, but I read on the corsair box 4 or 8 pin 12V rail and after taking a closer look at the connector noticed a small crease down the middle.

Tried to separate it and voila, split apart exactly like you said ;)  Thank you SOO much for the help everyone!! I was the only guy in my group of friends that did a build before, so was really bummed out I was letting em down after all hyping up how easy it is lol But I learned something from it so that's good :D 

Oh and @jsc, thanks for the tip on tying back the connector to avoid grounding it, I'll be sure to do that today!

Thanks again everyone!!!
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July 24, 2011 1:41:31 AM

Best answer selected by Blitzace.
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July 12, 2012 8:11:32 PM

This thread has helped me a ton (and saved me what I thought was going to be a huge waste of time and shipping costs replacing a PSU), and I've learned something new. Just dropping a line to say thanks to all contributors.
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September 11, 2013 8:14:10 AM

I just want to thank everyone who helped the OP, I had the same situation and was about to return the power supply. A quick google search led me right to this forum and saved me from a major headache!

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January 24, 2014 3:09:08 PM

jsc said:
The Corsair PSU's do not have an 8 pin CPU power connector. They have a "4+4" connector that can be split. Separate the two halves and tie one back out of the way.

That red circled part that the 8 pin connector touches is an electrolytic capacitor. The metal case is at ground potential. If the wrong part of the connector touches it, you could short 12 volts directly to ground. Undesirable. :) 



As someone who has built quite a few PC's in my time, I was perplexed for about 20 minutes because after finally laying the replacement PSU next to the system to review how I was going to route the wires on this Dell Proprietary XPS 410 unit I had just then realized that the motherboard had only a 4 pin 12v connector and the Corsair TX650m had an 8 pin. I spent 10 minutes looking online for a converter cable and then I typed in "Mobo has 4-pin 12V connector, but PSU has 8-pin. What Can I do" and low and behold this thread came up. Then I notice someone stating that "The Corsair PSU's do not have an 8 pin CPU power connector. They have a "4+4" connector that can be split. Separate the two halves and tie one back out of the way." I immediately got up from the computer so sure of myself that this could not be true because I had held the damn 8 pin connector in my hand for 5 minutes eyeballing the mobo and the connector and then back again. I was sure of myself in that moment that this poster was wrong I was already devising my response in my head to this person. I walked back into the back bedroom and looked at the Corsair PSU, found the 8 pin plug and went "Oh Shit", he was right!!!

SO this post is an apology before the fact that you were definitely right and I thank you so much for enlightening me in a moment of frustration. You truly can learn something new everyday, if your willing to open your eyes and ears.

So Thank You JSC, you made my day!
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May 3, 2014 7:51:11 PM

Same thing 8 pin Corsair 4 pin on mobo. This thread saved me a lot of headaches
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