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PSU 4-pin cpu rail to 8-pin mobo?

Last response: in Systems
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July 6, 2012 8:38:29 PM

I am currently doing a new computer build and I discovered that while the motherboard has an 8-pin connector for the cpu, the powersupply has two 4-pin connectors. One of these fits into the left side of the 8-pin connector, but the other does not fit the right side. I am inclined to believe that powering the cpu on the one 4-pin will be okay for a couple reasons. First, the motherboard manual specifically says:
Quote:
DO NOT forget to connect the 4-pin/8-pin ATX +12V Power Plug.

And the psu spec lists:
Quote:
1 x 4+4 Pin ATX12V/EPS12V

(Although I'm not certain whether that specifies that each 4-pin connector carries 12 volts or if they have a combined voltage of 12 - in which case there may not be enough power to the cpu from just the one)

So is my inclination to use the one 4-pin in the 8-pin mobo connector safe? Or do I need to find myself a new power supply?
July 6, 2012 9:08:00 PM

Oh and my cpu is an Ivy Bridge i5 for reference.
And to rephrase the initial description, the other 4-pin does not match the shapes of the right side of the 8-pin but it will fit in without any extra force.
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a b B Homebuilt system
a b à CPUs
a b V Motherboard
July 6, 2012 9:13:07 PM

ShadesOfGrey00 said:
Oh and my cpu is an Ivy Bridge i5 for reference.
And to rephrase the initial description, the other 4-pin does not match the shapes of the right side of the 8-pin but it will fit in without any extra force.

So the problem isn't that it won't fit, it's that you're concerned that the keys don't match
That's not an issue, the 4+4 connector is designed so that either side will work on a 4 pin header without having to match up the keys ( K.I.S.S. )
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July 6, 2012 9:20:02 PM

So I should plug both 4-pin connectors from the psu into the one 8-pin connector on the motherboard even though the right 4-pin doesn't match the shapes?
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a b B Homebuilt system
a b à CPUs
a b V Motherboard
July 6, 2012 9:25:27 PM

Yes
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July 6, 2012 11:11:53 PM

So I went ahead and connected both 4-pins to the 8-pin and hooked up the machine for first boot. When I hit the power button, the memOK led lit up red for a second before going out and the cpu fan jerked and stopped a couple times (after the other fans had started) before it started spinning at full speed. However, it did proceed to load the UEFI BIOS without problems and the memOK tuning reported success. I have tried booting a number of times and each time the exact same sequence occurs. Should I be concerned that the memOK led flashes and the heatsink fan jerks at boot? Or does the fact that everything proceeds normally mean its okay?
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