How to hook up power supply to WRX90E-SAGE for multi-GPU setup?

I am currently building a PC based on the WRX90E-SAGE motherboard, and I’m unclear on the proper way to hook up the power cables from the PSU. The information in the manual is very sparse, and I’m worried I’m gonna hook something up wrong and damage my hardware… I am going to be running 2 GPUs (RTX 4090) and an AMD 7965WX CPU, and I am using an EVGA Supernova G+ 1600W PSU.

So basically my questions are:

  1. For the CPU, should I be connecting the cable from PSU port CPU1 —> CPU 12V1_1 on the motherboard? What are the other CPU ports for? (the other ports are called CPU_12V(2)_1, PCIE_CPU_12V_1, PCI_CPU_12V_2) … Given that there is only one CPU socket on the motherboard, I don’t understand why there are two CPU power ports? Also, am I correct to assume that I should be using CPU_12V(1)_1 instead of any of the other ports?

  2. As far as the GPU, I am using dual RTX 4090s as I mentioned above, so I noticed this section in the manual:

When installing two or more graphics cards ensure to connect the PCIE_8P_PWR
connector(s). If the PCIE_8P_PWR connector(s) are not connected, a BIOS prompt will
appear and will remain until you have connected the PCIE_8P_PWR connector(s).

I am not understanding where I am supposed to connect these to the PSU, and what kind of cables to use. I already have power from the PSU going directly to the GPUs (4 x 8 pin PCI → 12VHPWR port for each card). Can someone explain to me what these PCI_8P_PWR ports are doing exactly?

I only have one additional VGA slot remaining on my power supply (the other 8 are being taken up by the two GPUs, each of which use 4 x 8 pin ports).

Can I just use one of the 2 x 6+2 PCIe cables that came with my PSU, and plug it into the remaining VGA port on the PSU and then plug both of the 6+2 connectors into the PCI_8P_PWR ports on the motherboard?

Just in case anyone else comes here looking for an answer, I figured this out after a bunch more digging online:

  1. Because the CPU power ports supply 300W, and the AMD 7965WX can draw up to 350W, you actually want to connect power to BOTH CPU_12V ports on the motherboard (the PCIE_CPU ports are only for if you’re using dual PSUs). So you will need 2 separate CPU power cables from your PSU to the motherboard.

  2. The PCI_8P_PWR ports are to provide supplementary power to the PCI slots, each of which can potentially draw up to 75W of power, according to the PCI standard. The RTX 4090s each have their own power being directly supplied from the PSU via the 12VHPWR connector (4 x 150W 8 Pin PCI cables) … but they still will draw a small amount of power from the PCI slot as well. So you will want to hook up both of the PCI_8P_PWR ports to your PSU as well. You can power these using a VGA/PCI cable.

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Yes, use both CPU_12V(1),(2) ports to supply extra 12V to the cpu because it is a real heavy power user.

If running multiple gpus as you are, always best to augment the standard PCIe 12V power cables directly connected to each gpu with some additional power to PCIE slots default 75W. As again, the gpus are heavy power users which spike power usage frequently. Don’t want the PCIE 12V voltage to sag and cause gpu errors or system crashes.

The PCIE power augmentation connector uses the standard VGA/PCIE power cables and ports on the power supply, NOT the CPU ATX_V1/V2 port cables.

The CPU and PCI cables are pinned out differently with 12V on one side of the connector reversed on the other type of cable. The connectors are keyed differently so you should not be able to incorrectly install the wrong cable to the connector unless you force something.

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