Can I safely use a PSU with an ATX 12v 4-pin for a board that has a EPS 12v 8-pin?

Information:

Page 16 of the manual to the motherboard says that the 8-pin connector is for supplying power to the CPU.

Method 1:

If you look at the pinout of the 8-pin socket and the 4-pin cable (figures 1 and 2 below respectively), you will notice that physically, it should be compatible. I found a page (figure 3) that indicates that it can be done, but strongly advises using a proper 8-pin cable. This makes sense because the connector is generally for providing the CPU with extra power (as opposed to any power), so while it may work, the system may suddenly shut down if CPU usage goes up to 100% (eg while doing a virus-scan, watching YouTube videos, etc.)

Method 2:

Another option I have found is some discussions (like this one) about using an adapter (figure 4) to connect the 4-pin cable to both halves of the 8-pin connector. In fact, there are plenty such adapters on eBay for as little as $1 (and free shipping). Newegg also has a couple. Of course the problem with this method is the same as the previous one in that there is no additional power being supplied; this method simply splits the power from one source across the two halves of the connector.

Like you said, a Molex-to-8pin adapter is a good option too. There are different ones available which either split a single cable across the two halves of the 8-pin connector (which is generally not going to be a problem since that is what happens when you plug the three or four connectors on one cable into multiple drives, etc. anyway). There are others (figure 5) that have two separate Molex connectors (one for each half of the 8-pin) which you can plug into Molex connectors from different cables from the PSU for extra peace of mind. These are fairly cheap too (~$2 with shipping). It also has similarly good reviews.

In fact, there are also 6-pin PCI-E to 8-pin ATX12V adapters as well, and probably others (though you indicated that the PSU does not have this).

Recommendation:

The difference between the two methods gets to be somewhat complicated if you are not familiar with electronic engineering, but suffice it to say that method two is the better one in most circumstances. Using a PSU with an actual, dedicated 8-pin cable is the best solution of course, but if you look at the reviews at Newegg for the adapters, you will see that all of the reviews are positive, indicating that an adapter will likely be a good way to solve this problem for next to nothing.

Figure 1: 8-pin EPS ATX_12v motherboard connector

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Figure 2: 4-pin ATX 12v auxiliary connector

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Figure 3: Using a 4-pin cable in an 8-pin plug

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Figure 4: 4-pin to 8-pin ATX 12V adapter

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Figure 5: Molex to 8-pin adapter

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Synetech

Posted 2012-02-05T04:36:39.843

Reputation: 63 242

Many mainboard manuals explicitly state that method 1 (4-pin plug in one half of 8-pin socket) is supported. For example, from an ASRock manual: "Though this motherboard provides 8-pin ATX 12V power connector, it can still work if you adopt a traditional 4-pin ATX 12V power supply. To use the 4-pin ATX power supply, please plug your power supply along with Pin 1 and Pin 5." Likewise for the 24-pin ATX connector. I've also seen mainboards with a special cap for the unused 4 pins. – nwellnhof – 2014-10-11T21:14:43.130

That is the most comprehensive and complete answer I could have ever gotten. THANK YOU. That answers exactly what I was thinking. +1 to you! Edit: What about if I use this instead? Would this be even more ideal since it converts both the 4-pin + molex into a proper 8-pin? http://www.newegg.com/Product/Product.aspx?Item=N82E16812200459

– White Phoenix – 2012-02-05T07:52:55.730

1Yes. That is good too. I’ve added more detail to the answer. – Synetech – 2012-02-05T18:41:21.693

Isn't that 2 4-pin molex to 8-pin adapter meant for PCI-E cards that require 8-pins and not for EPS 12v 8-pin? The one I linked converts the ATX 12v 4-pin + a molex 4-pin into an EPS 12v 8-pin. – White Phoenix – 2012-02-06T04:26:12.383

1If you look closely, you’ll see that the pinout is the same (it will fit because it is round,square,square,round; square,round,round,square). – Synetech – 2012-02-06T04:30:46.360

@Synetch Gotcha. Thank you for the informative post. The only converter I could find was the one on Newegg for the ATX 12v 4 pin + 1 4-pin molex. Could you point me to where you found this picture and a site that sells it? – White Phoenix – 2012-02-07T22:31:14.137

Which one? The 1x/2x Molex to 8-pin? You can get them on eBay for <$2 including shipping.

– Synetech – 2012-02-07T22:34:15.793

I have a weird problem with this situation: the sound card and TV card in PCI socket doesn't work when I use 4-pin power supply connector connected to a 8-pin socket. Do I need a 4-pin to 8-pin adapter/a new PSU to make it work? Old motherboard: Gigabyte GA-H55M-D2H (4-pin), New motherboard: Gigabyte GA-H87M-D3H (8-pin), Power supply: Coolmax V-350

– LiuYan 刘研 – 2014-05-10T03:14:48.493

@LiuYan刘研, Well your old motherboard only had a 4-pin auxiliary power connector while the new one has an 8-pin connector. You could try a 4-to-8 adapter like figure 4, but that won’t magically provide more power. If your cards are not working, then they are likely not getting enough power, so a simple adapter may not be enough. You would be better off either using a molex adapter like in figure 5, or getting a new PSU with the correct cables. – Synetech – 2014-05-11T01:59:38.677

@Synetech, I borrowed a power supply which has a 8-pin connector, installed it, powered on, and no luck, the PCI cards still not been detected (linux command lspci does show anything about it, when I use the 4-pin connector, sometimes, linux live CD can detect them(but making no sound)). Now I'm guessing if it's the heavy humidity (97%) caused the problem. This sound card (Creative Xtreme-Music) sometimes not working too in the old motherboard, I must replug it several times to make it work. – LiuYan 刘研 – 2014-05-13T02:18:00.907

It's actually caused by edge connector been oxidized which is highly related to the heavy humidity these days. Wiped the edge connector of PCI cards and re-plugged them, now they are all been detected now. BTW, I've damaged the old power supply (too noisy, opened it and cleaned it with wet papers, powered on, smoke appeared, oops), and bought a new power supply yesterday.

– LiuYan 刘研 – 2014-05-16T03:25:57.267

Can I safely use a PSU with an ATX 12v 4-pin for a board that has a EPS 12v 8-pin?

Answers