Can a 4 pin power connector supply ATX 12v 2x4 motherboard (i7-4790k)

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Caroline Beltran

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Feb 1, 2015
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I just bought a brand new i7-4790k CPU and a Gigabyte B85m-hd3 REFURBISHED motherboard. I was unaware that this motherboard came with an 8 pin CPU power cable and I bought a power supply unit with a 4 pin CPU power cable.

I've read online posts from various individuals saying that they got their system working just fine by plugging in the 4 pin cable into the 8 pin motherboard connector. All of these individuals used a different processor than mine.

I tried this and this is what happens:


  • CPU Fan attempts to rotate for a couple of seconds then stops. After a second, the process is repeated over and over.

  • PSU Fan successfully rotates for a couple of seconds then stops. Process repeated.

  • Power LED switch turns on and off for the duration corresponding with fan activity.

My main concern is that this motherboard (being refurbished) may be bad. I live in a remote location and typically order PC related items for delivery which takes a few days.

I read comments that the voltage should be the same for 4 and 8 pin connectors. My PSU is 500W and in fact I have a spare unused 500W PSU meaning that both power supply units are likely not bad.

Please advise


UPDATE: I added a system 'beep' speaker to the motherboard. When I power on the computer, you hear a quick 'click' instead of the usual beep when everything is OK. It almost sounds as if the computer does not have enough power to spin the Cpu fan or even power the system speaker properly.

 
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ko888
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SinxarKnights

SinxarKnights

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Look in the motherboard manual about it. If it is not mentioned it may require the 8 pin. But first if this is a new build attempt to reset the bios with the jumper then try it again with the bare minimum config. Without it being properly connected it is impossible to say if it is the motherboard or lack of power.

It would help we knew what motherboard you are using as well.

ed: I looked through the manual and it doesn't mention that it is compatible with the 4 pin only connector. So unless you happen to have a PSU sitting around with an 8 pin CPU connector, there is no way to be sure what is wrong with it if a BIOS reset doesn't fix it.
 
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Cons29

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Feb 10, 2010
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sorry for asking, but is the psu an old one? because the 8pin has been around for some time now, so psu's already come with it. and you have an i7, i mean, if you pair that with a good gpu (if ever you play games) then a good psu is needed, don't skimp on the psu, just my 2 cents
 
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ko888

ko888

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Feb 18, 2009
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Is the 4-pin ATX12V CPU Power Connector from the PSU plugged into the motherboard's CPU power connector socket as shown in green in the following image?
GIGABYTE_GA_B85_M_HD3_ATX12_V_CPU_Power_Connector.jpg
 
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Caroline Beltran

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KO888, that is correct, I have the 4 pin connector plugged into the green area (it will not fit into the non-colored side btw). I also tried what SinxarKnights suggested and reset the CMOS.
 
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Caroline Beltran

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One of the PSU is old (was working) and another is brand new (4 pin) unfortunately. I don't have a GPU because I don't play any games being the bitter person I am :0

My CPU is supposed to consume something like 84w so I think that a 500w supply is fine. What confuses me is that people have said that they are working using a 4 pin on 8 pin connector. I really shouldn't have purchased a refurbished motherboard because that adds more confusion into the mix.
 
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Caroline Beltran

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I tried the reset (short the clr_cmos) but still have the same issue. Bare minimum, just have the RAM, CPU/FAN and power push button cable set. For power, I have the ATX 12 pin and the CPU 4 pin connected.

With or without RAM, the same symptoms are observed. I changed the brand new RAM that I had ordered with an older 1.5v RAM that I had. No difference at all.

The PC Parts vendor indicated that the REFURBISHED motherboards were tested by experts before being repackaged but it makes me wonder why someone would return it in the first place.

UPDATE:

I read a post stating that the 4 pin connector supplies 75w and the i7-4790k uses 88w. This here may be the problem. I will need to put in an order for an 8 pin PSU.
 
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ko888

ko888

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I don't have any trust in Refurbished motherboards. You need to carefully check the CPU socket for any bent/user damaged contacts before purchasing it.

The ATX12V 4-pin CPU power connector should have no problem powering CPUs with up to 95W TDP. The +12V rail that is supplying the power to the 4-pin CPU power connector needs to have a continuous current rating of at least 16 Amps or greater.
 
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Caroline Beltran

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Feb 1, 2015
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Interesting suggestion so I looked into this and from what I've read, you only need a Haswell compatible power supply if you enable sleep or hibernation mode.
 
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Caroline Beltran

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Feb 1, 2015
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This is the first and last time I buy a refurbished motherboard even though there are no visible signs of damage something is wrong.

I ended driving a few hours to a local dealer and purchased the best that they had in stock which was an inferior brand motherboard with less features. I installed this motherboard and it immediately worked with my 4 pin power supply.

By the way, I took my PC and tried a power supply with 8 pins and the results were the same which means that the refurbished monitor although a good brand which I have used before, was junk! I'm quite upset that they tell you that the refurbished monitor was 'tested by experts'. Maybe experts in poking around with their cell phones...

I do want to thank everyone for helping me out with this issue.
 
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