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I was reading this article, and a question came to my mind.

8 pin EPS12V power cable

enter image description here

8 pin PCI Express power cable

enter image description here

Besides the name and the color, these 2 connectors look the same.

  • Is there a case where one should be used over the other?
  • Is there any difference between these 2 connectors?
  • Is the color of the connector a correct way to distinguish them?
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They are completely different.

The EPS connector is meant to supply power to a motherboard cpu socket while the PCI express connector is meant to supply power to a GPU.

You shouldn't be able to switch between them - the square and rounded off connectors are arranged such that you can't. Note the top left connector on the EPS 12V is squared off, while that on the PCIe is rounded off in the image before.Essentially differences like that are to prevent you from plugging in a PCIe connector into a EPS12V. There may be other differences, but I don't have these connectors on hand/

The power connectors are different - while they're both 12V (yellow) and ground (black) the row closer to the clip of the PCIe connector is ground, and the bottom is 12V, and its the other way around on the EPS 12V.

Here's a much bigger/better picture of them taken from the computer hardware chart done by Sonic840 on Deviantart (CC BY-SA)

enter image description here

Attempting to switch between them will result in physical damage, from attempting to fit physically different connectors and electrical damage, from reversing the power feeds to the device. I'd recommend inspecting the connectors (which are typically labelled), as well as the order/colour of the power cables connected to the connector in working out what a cable is. Connectors themselves however are not typically colour coded in any way.

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  • beat me to it, my answer heading for the trash can ;) +1 for Q & A, it's a question that gives good opportunity to clear up a possibly fatal [to the mobo] misconception.
    – Tetsujin
    Commented Dec 6, 2014 at 11:41
  • Is the color of the connector a convention? Or I should not trust that to identify them?
    – Enrique Moreno Tent
    Commented Dec 6, 2014 at 11:44
  • I wouldn't trust the colour. I'd examine the plug and socket, and the pci-e cable is usually labelled. More often than not 'cheaper' PSUs use that semi translucent white plastic, and 'premium' parts use black plastic in my experience.
    – Journeyman Geek ♦
    Commented Dec 6, 2014 at 11:47
  • @Dbugger Indeed, all connectors are usually the same color in a given PSU.
    – ntoskrnl
    Commented Dec 6, 2014 at 14:20
  • The reason for the difference is that EPS12V is an extension of a four-pin connector, while 8-pin PCIe is an extension of a six-pin connector.
    – Mark
    Commented Dec 6, 2014 at 21:44
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it should be said, as this generate a doubt for non used user, that all the sockets (on a modular power supply) that are marked CPU/ PCI-E are identical. One could think a part of them are for CPU (12V) and the rest for PCI-E. In fact it is the cable itself that swap 12V pins and GND pins to comply with the mother board pin arrangement.

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  • My new PSU (CORSAIR RM850e ) comes with four (PCI-E/CPU) ports. Which confused the hell out of me because I thought that they're incompatible with each other and vis versa. How-ever checking the cables they do swap 12V pins and GND pins to comply with the mother board pin arrangement.
    – Chad
    Commented Mar 20 at 2:23
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Unfortunatelly it's not true that you cannot connect PCIe 8-pin plug to EPS-12V (EATX) motherboard slot. It might be only an exception found with FSP PSU, but a single difference in one male pin on PCIe connector allows to plug your PSU totally wrong.

PCIe and EPS-12V FSP PSU plugs comparison against GPU PCIe socket and motherboard EPS-12V socket:

Picture.

See the picture: top left GPU PCIe socket, top right PCIe plug, bottom left motherboard EPS socket, bottom right EPS plug. As you can see, the top right pin of PCIe plug is rounded which allows to accidentally plug it to motherboard EPS socket.

This way one could easily destroy motherboard/CPU components. I don't know if this is the only PSU having this flaw, I haven't seen PCIe plug with rounded top right pin on Corsair PSUs.

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  • Look again closer: the top right pin of the PCIe connector has a little "Wing" which gives it a P shape. It will not fit into the EPS socket.
    – 1NN
    Commented Jun 24 at 17:25
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Some cables come in all black, especially those come with power supply for cosmetic and some in all yellow anyway, you can't actually rely on the color.

Despite the color of the wires:

  • You can't connect male EPS-12V to female PCI-E 8-pin because 1 male pin of EPS is square and its rounded on PCI-E.
  • You can't connect male PCI-E 8-pin to EPS-12V because 2 male pins on PCI-E as the top edge joined together and the corresponding pins on PCI-E does not have a slit for that.

    As said, I have successfully converted EPS extension cable for PCI-E by swapping the color wires and cut a slit on the female connector.

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