Mixing up modular PSUs is common.
Mixing up modular PSUs is common.
They use the same connector on the power supply side, because it's possible to do it. pci-e uses 3 12v wires and 5 ground wires. cpu uses 4 12v wires and 4 ground wires. So the connector on the power supply has 4 12v pins, and 4 ground pins. The pci-e cable will connect the 5th ground wire with the 4th wire to one of the 4 pins and just won't connect anything to the 4th 12v pin. The cpu cable is straight forward, 4 12v wires go to 4 12v pins, 4 ground wires go to 4 ground pins. There is a difference between CPU (EPS) connector that plugs in motherboard, and the pci-e connector that plugs in video card. One of them has the 12v wires on the side with the retaining clip , the other one has the 12v on the opposite side. In order for idiots to not plug them the wrong way or in the wrong place, the connectors are KEYED. If you look at the actual pins, you will see that the plastic has certain shape. Some pins in the connector on motherboard will be square, some will have a D shape.. if you try to plug it in the wrong place it will not fit, it won't go easily. This is how it looks on motherboard : and these are on the video card ... note that D shapes are in different locations, so you wouldn't be able to plug CPU connector into pci-e 8 pin connector. Pin 5 (bottom left) on connector would not go into the bottom right pci-e 5th pin hole, due to its shape... The CPU connector on the power supply cable may not match 100% when it comes to the keying, because it's slightly changed by the manufacturer from the standard so that someone can plug either of the 4 pin parts (when the 8 pin is separated into 2 4 pin pieces) into a 4 pin header on the motherboard, if the motherboard has only a 4 pin cpu connector / header.
Appreciate the clear explanation. By comparing squares and oval-squares, it’s easy to see how they differ. Your question about the CPU cable with two headers is helpful—likely it serves both length and connectivity purposes. Your motherboard supports two slots for eight pins, so leaving one open after insertion makes sense.
Certainly! Here’s a rephrased version of your text:
Some motherboards feature two 8-pin connectors, typical for dual socket models aimed at heavy overclocking. Two CPU socket boards commonly use separate 8-pin connectors, one per socket, even though each chip may draw minimal power. For various reasons, these connectors are designed to handle around 300 watts (four pairs times seven amps per pair equals roughly 336 watts), yet each CPU usually consumes only 100-150 watts. This ensures safe operation and allows two processors to share a single power cable. On the power supply side, each wire pair can safely carry over 10A, though the connectors themselves are rated for at least 9A (providing a minimum of 432 watts). Some manufacturers opted for a single 8-pin connector on the cable and split the second one along the line, making it compatible with older boards that still used four-pin headers. This setup lets you use an 8-pin header on a power supply while concealing the second connector inside the motherboard.
I see your point. The setup has two sets of pins: one side has 8 pins and the other has 16 pins. You connected 1*8 to the PSU, but the remaining 2*8 on the other end—should I connect just one of those pins while leaving the rest unconnected? Or should I connect both ends fully? It seems like it would limit the power output to around 320W regardless.
Choose one 8 pin connector or use both if your motherboard supports it. The power supply unit doesn’t matter and the motherboard won’t either. If only one 8 pin is available, connect the nearest one to the PSU and leave the other unused. On boards with two 8 pin headers, it’s better to add a second cable between the PSU and the second header, as more wires reduce losses and heat. The current spreads out over more wires, which improves efficiency. However, if you’re not doing heavy overclocking, you likely don’t need the extra connection.