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EVGA PSUs: Are CPU and VGA ports interchangeable?

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retsof81
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2021/07/23 23:17:32 (permalink)
I am researching parts for a new build and would like to use an EVGA 850 SLX PSU with an RTX 3080. The 3080 has three 8-pin connectors but the SLX PSU only had two VGA ports. I would like to avoid splitting connectors to the GPU, so can I use one of the CPU ports for a total of three dedicated PSU ports for the GPU (2 VGA ports and 1 CPU port)? 
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    a213m
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    Re: EVGA PSUs: Are CPU and VGA ports interchangeable? 2021/07/24 01:27:33 (permalink)
    This PSU? https://www.evga.com/products/product.aspx?pn=123-GM-0850-X1
     

     
    No. CPU uses 4x12V+4xGND, VGA uses 3x12V+5xGND, and the PSU sockets are keyed, so you can't use wrong ports. Howerver, PCI-e power cables come with 2 plugs, so you'll be fine.
     


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    retsof81
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    Re: EVGA PSUs: Are CPU and VGA ports interchangeable? 2021/07/24 07:25:17 (permalink)
    Yep, that's it!
    Thanks for clarifying. Unfortunate that I cannot have a dedicated port/cable for each GPU socket, but I guess its all relative in terms of power delivery. 
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    retsof81
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    Re: EVGA PSUs: Are CPU and VGA ports interchangeable? 2021/07/26 12:32:49 (permalink)
    FYI... I did more research and found out the following:
    • The need for three GPU 8-pin sockets has to do with a PCI-e specification where each 8-pin peripheral socket cannot exceed 150w, regardless of cable quality and/or PSU capability.
    • The same specification does not limit how many watts are supplied from the PSU, which means a single PSU socket can theoretically supply 300w across a single cable with two 8-pin connectors at the end. 
    • In terms of the RTX 3080, my understanding is it's capped at 380w (I had a friend verify this on their stock 3080, running a benchmark).
    Given the PCI-e slot already provides 75w, the two cables would need to provide the remaining 305w. Per a213m's response, there would be no issue using three 8-pin connectors over two PSU cables -- minimal draw over 150w per PSU VGA port (5w over at best). 
     
    Let me know if there is anything off with my research or assumptions. Thx!
    post edited by retsof81 - 2021/07/26 12:36:25
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    tt092478
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    Re: EVGA PSUs: Are CPU and VGA ports interchangeable? 2022/03/12 09:01:31 (permalink)
    Sorry for resurrecting this thread. My mobo has 1 8 pin and 1 4 pin connection required (crosshair hero 8). Can I use any part of 4 pin from cpu 2 connection? As they split in two 4 pin on the other side.
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