For those dual-8-pin CPU power mobos, if your PSU only has one 4+4/8-pin, or you've lost the cable, but have a spare PCI-E power cable.

[VirtualLarry]

Are you a human?

www.newegg.com

I haven't tested this myself, but I've read on here (from Markfw and others) about X570 (and EPYC?) boards that require dual 8-pin CPU power, and if you don't plug in BOTH of them, you have booting problems.

This little adapter from Athena Power may solve that issue. It converts between a 6-pin PCI-E power cable, to a 4+4 CPU power cable.

 

[Fardringle]

It may provide the right number of pins, but I'm not sure it will supply the power that the motherboard/CPU wants. A proper 4-PIN CPU power plug is rated to provide up to 155 watts and an 8-PIN CPU power cable is rated to provide up to 235 watts. A PCI-E power plug is rated to proved up to 75 watts. If the CPU tries to draw 155 or 235 watts through a PCI-E power adapter, it probably isn't going to work very well...

 

[VirtualLarry]

Well, I think in actual practice, it should be OK for those X570 boards that need TWO EPS12V or an EPS12V and an ATX12V (2x2-pin) boards. As long as the primary CPU power is on the hard-wired PSU connector, it's probably OK.

Btw, the PCI-E 6-pin CAN carry at least 150W safely,. as there is no difference in the current-carrying wires between a PCI-E 6-pin and 6+2 pin. The two extra pins are for "Sense".

 

[Ajay]

Btw, the PCI-E 6-pin CAN carry at least 150W safely,. as there is no difference in the current-carrying wires between a PCI-E 6-pin and 6+2 pin. The two extra pins are for "Sense".

Well, up to 300W, if the wires are the correct gauge. Thought the two extra pins were ground?

 

[mindless1]

A more common limitation is 6A current per (positive, assuming same # of grounds) connection pin, but all bets are off if the adapter uses Chinesium pins of unknown quality.

A decent quality 6-pin PCI-E should be capable of roughly 3 * 6A *12V = 216W.

 

[Markfw]

Are you a human?

www.newegg.com

I haven't tested this myself, but I've read on here (from Markfw and others) about X570 (and EPYC?) boards that require dual 8-pin CPU power, and if you don't plug in BOTH of them, you have booting problems.

This little adapter from Athena Power may solve that issue. It converts between a 6-pin PCI-E power cable, to a 4+4 CPU power cable.

I had an x370 board running one of my 3900x's. It worked OK for a little while, then kept shutting down. If the board has 2 connectors, you better use them, or you are asking for trouble.

Edit: That adapter looks like it might be the answer, but NOT 150 watt. That with all pins powered and ony 4 of the 6 are.

 

[mindless1]

^ ?? It's 6 pins (3 powered per a PCI-E 6 pin and the other 3 pins being ground) into 8 pins on 2x connectors, 4 powered. Why would that drop the wattage compared to what the PCI-E connector was capable of (150W+) by itself?

 

[Markfw]

^ ?? It's 6 pins (3 powered per a PCI-E 6 pin and the other 3 pins being ground) into 8 pins on 2x connectors, 4 powered. Why would that drop the wattage?

Got me, just a guess. If you aren't using the correct connector, not sure what happens. I don;t take chances.

 

[Fanatical Meat]

My 3800x & x570 steel legend wouldn’t boot without the extra power cable connected. I too had the I lost the extra cable problem.
Per my reading at the time you shouldn’t mix the other cables because the layout looks the same but it isn’t and that can damage the board.
I ordered a cable from amazon. I forgot the brand but they are a package of braided connectors made for people who want to show off with their windowed cases. Cable was rated for my power supply.