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MB power supply using ATX 12V plug?

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June 2, 2011 11:14:23 PM

Hello,
My son, in the Air Force, was called overseas, leaving me with a partially finished PC. The problem is no power to the motherboard. The manual says to use an 8 pin cable to power the ATX 12V plug. The problem is that the modular power supply has a cable with the correct 8 pin connector for this but the other end is a PCI-E plug with a 6+2 plug. This plug doesn't fit anywhere with all 8 pins. It does fit into the power supply if I only use the fixed 6 pin plug, leaving the loose 2 pin connector unplugged. Right now, there isn't any power to the MB. To call me inexperienced is the understatement of the year.

Any help getting power to the MB?

Thank you,
grumpa

grumpa72@gmail.
a b V Motherboard
June 3, 2011 1:17:18 AM

grumpa72 -- first of all, best wishes for your son's successful deployment and safe return. I'm sure you'll find that Tom's forums will get you through at least this issue.

#2 -- would you please provide the brand and models for both the motherboard and the power supply?
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a b Ĉ ASUS
a b ) Power supply
a c 107 V Motherboard
June 3, 2011 4:01:14 AM

DO NOT, I repeat, do not plug that 6+2 PCIe connector into the mainboard.

The power supply will have a specific 8-pin plug labeled ATX12V or EPS12V to power the mainboard. It might be in a 4+4 arrangement. Or, if it's an older power supply, it might have a 4-pin ATX12V plug instead instead of the 8-pin.
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June 3, 2011 6:22:39 PM

I suppose that knowing the power supply and motherboard would help.

Mother board is MB ASROCK|P67 EXTREME4 (B3) P67 R and the power supply is PSU CORSAIR|CMPSU-850HX 850W RT. My son ordered all the components and says that these are good and relatively high on the food chain.

My issue with the modular cables is that there is a cable with a blue 8 pin plug that fits in the ATX 12V plug on the MB. That same blue plug fits into the back of the power supply. On the other end is the PCI-E 6+2 plug that I mentioned in the original post. Common sense tells me that I need a power plug that has the same 8 pin plug setup on both ends. From what little I have read about the PCI-E plugs is that they are for the other components like HD, DVD, etc. My Corsair power supply doesn't have anything that seems to fit for this ATX 12V plug AND the power supply back side.

I am really working in the dark here. I have zero experience dealing with computer components and such - the most I have done in the past is to add a second HD and swap out a faulty CD burner. The PCI-E cables are all new to me.

Shadows, I haven't yet plugged the 6+2 PCI-E cable into anything since it doesn't fit anywhere (well, at least I am understanding where it goes).
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a b V Motherboard
June 3, 2011 6:34:13 PM

grumpa72 said:
I suppose that knowing the power supply and motherboard would help.

Mother board is MB ASROCK|P67 EXTREME4 (B3) P67 R and the power supply is PSU CORSAIR|CMPSU-850HX 850W RT. My son ordered all the components and says that these are good and relatively high on the food chain.


Yeah, your board and power supply are considered excellent and reliable performers.

For the PSU, I downloaded the manual.

In the manual, skip to page 5 (the adobe page 5, not the page marked on the sheet).

There are a few pictures of connectors. You're currently looking at the "PCI-Express 8-pin & 6-pin compatible." This plugs in to video cards.

You want the "EPS/ATX12V 8-pin & 4-pin compatible." This is what you're going to plug into your motherboard in the jack nearby the CPU. Now skip to page 7 of the PDF document. Look at step 6:

Quote:
6) The 8-pin EPS12V connector can be separated and used as a P4 / 4-pin ATX12V connector. If your motherboard is equipped with a P4 / 4-pin ATX12V socket instead of an 8-pin EPS12V socket, simply separate the 8-pin EPS12V connector into two and plug one of the halves into your motherboard. It does not matter which half you choose.

7) If your motherboard has an 8-pin EPS12V socket, connect the 8-pin EPS12V
connector directly to your motherboard. Some motherboards have two 8-pin
EPS12V sockets. If your motherboard has two 8-pin EPS12V sockets then ensure you connect 8-pin EPS12V cables to both of them.


You should follow step 7, because the ASRock Extreme4 has a 8-pin EPS12V socket located near the processor.

It may be difficult to tell the difference between the 6+2-pin PCIe power connectors and the 8-pin EPS12v connector. The way to tell the difference in the case of this PSU is to note that it ships with 6 6+2 pin PCIe power connectors with only one 8-pin EPS12v connector for the HX850.
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a b Ĉ ASUS
a b ) Power supply
a c 107 V Motherboard
June 4, 2011 1:09:41 AM

I looked at an online review of the 850HX power supply. The correct cable to use for the 8-pin mainboard connection is not one of the modular cables. It is permanently attached to the PSU, and it is arranged as a 4+4 pin.

The blue plugs you are talking about are meant to be plugged into the blue connections on the PSU. You shouldn't need to use those though -- they are only needed if you have more than one graphics card.
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June 4, 2011 2:25:20 AM

Thank you for your input. I do recall that tha PSU had 4 pin plugs but I didn't know enough about them to assume that they were used in a 4+4 configuration. When I get home, I will check this out.

Since you were all so good at this, can someone explain why the PSU 24 pin connector only uses 20 pins and I split off the 4 pin module? Next question, there is a nice dual video card, ASUS/EAH6950DC/2DI4S/2DR, that takes one of the fixed cables from the PSU. once that cable is installed, there is a 6 pin female plug still open. That plug will take the 6pin portion of the 6+2 PCI-E plug. Should I be plugging that in and, if so, is that because of extra power needed for this video card?

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a b Ĉ ASUS
a b ) Power supply
a c 107 V Motherboard
June 4, 2011 5:23:41 AM

Most power supplies come with the 24-pin main power connector split into a 20-pin and a 4-pin because there are some older boards that only need a 20-pin main power connection. All newer boards require the full 24-pin, plus other power connections as well.

The PCIe slot itself can only supply 75W of power to the graphics card. The extra power sockets on the graphics card are there because modern GPUs need much more than 75W. You should plug both of the extra plugs in. Otherwise, the graphics card won't have enough power and it won't boot up.
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June 5, 2011 11:48:59 AM

Leaps-from-Shadows said:
DO NOT, I repeat, do not plug that 6+2 PCIe connector into the mainboard.

The power supply will have a specific 8-pin plug labeled ATX12V or EPS12V to power the mainboard. It might be in a 4+4 arrangement. Or, if it's an older power supply, it might have a 4-pin ATX12V plug instead instead of the 8-pin.


Out of pure cuoriosity, what will I burn IF I would put a PCIe 6+2 into the Mobo for CPU power?

Only the CPU or also the Mobo?
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a b Ĉ ASUS
a b ) Power supply
a c 107 V Motherboard
June 6, 2011 2:33:56 AM

If you damage anything, it would most likely be the power supply. It has safeguards for things like that, but damage can still occur.
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June 8, 2011 12:27:32 PM

Got the beast running. It was indeed the power supply to the CPU as you have said. How I could be so uninformed is beyond me. Software is in.

Thank you all for your help.
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March 23, 2012 1:43:38 PM

Leaps-from-Shadows said:
DO NOT, I repeat, do not plug that 6+2 PCIe connector into the mainboard.

The power supply will have a specific 8-pin plug labeled ATX12V or EPS12V to power the mainboard. It might be in a 4+4 arrangement. Or, if it's an older power supply, it might have a 4-pin ATX12V plug instead instead of the 8-pin.



I have the same problem. I have 2, 4 pin connecters that are banded together but I still have a problem as I don't think they are the ATX 12V as the pins aren't the same shape for the holes on the main board.

I have an ASUS M5A97 moterboard and a Cooler Master case & Power Supply.

I have contacted Cooler Master and plan to contact ASUS as well.

What Power Supplies have the 8 Pin 12V ATX connecter?

This stinks as I think I'm going to have to send in the power supply for one that works with my board :( !! One thing to another!!

Any suggestions?
I think it'd be bad to force the 2, 4 Pin connecters into the 8 pin socket. There is a reason that the pins are the shape that they are. I just wonder why Cooler Master didn't put the right ponnecters on their power supply????
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March 23, 2012 3:24:36 PM

I found a solution to anyone else who runs into this problem.

StarTech EPS48ADAP 6in 4 Pin to 8 Pin EPS Power Adapter with LP4 Item #: N82E16812200459
Only $6.99 and has the regular 4 pin adapter to 8 pin motherboard 12V ATX plug with the correct pin arrangement. This is much easier than trying to find and swap power supplies.

Peace and Blessings always,

Not as newbie as I thought I was but one more process in the build.. You live and you learn I guess.. :)  :sarcastic: 
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