Question New Graphics Card has 3x8 pin PCIE ports. I only have two 8 pin PCIE connectors.

Jul 10, 2021
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Hello, this is my first ever post in Tom's Forum.

On the basis of a build I made on PC Part Picker https://pcpartpicker.com/list/4XT6Hz, with "No issues or incompatibilities found." I had assumed that upgrading my graphics card to the EVGA RTX 3090 FTW3 Ultra would be safe and possible. As I took the card out of the box, I noticed there were 3 8 pin PCIE slots on the card and I only had 2 8 pin PCIE cords coming from my Corsair RMX 750 PSU. Not wanting to screw anything up, I took the card out of my rig and put it back in the box it came in in the mail. Just in case I may have to return it. But is it possible to use 2 8 pin PCIE cords with 3 8 pin ports? If not, is there a cable I can buy? Based on my searches, I can't find a cable like this on Amazon, Newegg, or anywhere else. Is there a PSU I could get to make this work?

Here is an image of my issue.
 
Jul 6, 2021
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You need to connect all 3.

According to your PSU's page, it has 4 PCIe connectors. Do you still have all the cables that came with it?
Usually when they say 4 PCIe connectors, they come with 2 (6+2) cables with another (6+2) daisy chained to it. That may force the cable to draw more power than it is designed to. Unless its AWG 16, i would buy a new PSU tbh. You shouldnt add cables to a PSU that it doesnt come with.

For example: This is the PSU i have. It says it comes with 6 PCIe connectors, but i know for a fact that it comes with 3 PCIe cables with pigtails. I still have the box with the cables left over and everything.
 

mikewinddale

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Dec 22, 2016
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Usually when they say 4 PCIe connectors, they come with 2 (6+2) cables with another (6+2) daisy chained to it. That may force the cable to draw more power than it is designed to. Unless its AWG 16, i would buy a new PSU tbh. You shouldnt add cables to a PSU that it doesnt come with.
Okay, serious question: is the wire gauge not typically low enough? I assumed that if a PCIe cable had two connectors, that the gauge was low enough to support the total power draw. Is that not the case?

And if not, then what is the purpose of the second connector, if the gauge is only enough to support one connector?
 
Jul 6, 2021
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Not necesarily. Depends on the manufacturer. Some PCIe 6+2 come in 18 AWG and others with 16 AWG.

If the daisy chain is ok to use or not depends on 2 factors: the total power draw of the GPU and the rating of the cable. A GPU could draw enough power to need 8 + 6 and still low enough to be below the rating or draw a ton of power and use like 8+8 (the max amount of pins you get from a 6+2 with daisy chain) and burn the cable.

Or the cable could be of lower AWG like 16 or 14 and have a good enough rating to connect whatever into it.
 

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