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Thread: Ryzen 2700x / x470 and the additional 4 pin power

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    Default Ryzen 2700x / x470 and the additional 4 pin power

    Just got my Ryzen 2700x and a new x470 motherboard and I realize that the motherboard takes both an 8 pin and a 4 pin cpu cable. Unfortunately, I just bought a Seasonic Prime Ultra Gold 550w a few months back and it has the 8 pin, but not the 4 pin connector. Not sure how I screwed this up, but do I need to get a more powerful PSU, or can I purchase the correct cable on its own? Any suggestions as to which PSU I should get? Build includes the above cpu/MB plus 16GB DDR4, one 1070ti, two NVME drives, two ssd's and a normal HD.

    I realize I could just be overthinking this too...

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    Just use the 8-pin. You'll be fine.

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    The Ryzen processors don't use a lot of power... they peak at around 120A @ 1.3-1.4v ... so maybe 150w at most. Even with lousy efficiency on the VRM, you're not drawing more than 200w from the connector.

    The connector itself can do around 7A per pair of wires if you want to stick to the standard, so that's 12v x 4 pairs x 7A = ~ 336w
    If you don't care about the ATX standard, the physical connector contacts are rated by Molex at around 9A and the wires themselves are think enough to handle more than 10A without significant voltage drops.

    So basically the Ryzen processor will barely go over half the capabilities of the 8pin cpu connector, there's no need to use the 4 pin cpu connector.

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    ehume (07-23-2018)

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    Quote Originally Posted by mariush View Post
    The Ryzen processors don't use a lot of power... they peak at around 120A @ 1.3-1.4v ... so maybe 150w at most. Even with lousy efficiency on the VRM, you're not drawing more than 200w from the connector.

    The connector itself can do around 7A per pair of wires if you want to stick to the standard, so that's 12v x 4 pairs x 7A = ~ 336w
    If you don't care about the ATX standard, the physical connector contacts are rated by Molex at around 9A and the wires themselves are think enough to handle more than 10A without significant voltage drops.

    So basically the Ryzen processor will barely go over half the capabilities of the 8pin cpu connector, there's no need to use the 4 pin cpu connector.
    But isn't the four-pin connector used for the PCIe plane?
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    Quote Originally Posted by ehume View Post
    But isn't the four-pin connector used for the PCIe plane?
    Generally no, if the motherboard needs more PCIe power for 4 way SLI/XFire then it usually uses a 6 pin PCIe cable (usually near the bottom of the board), though I have also seen MOLEX connectors used. The extra EPS connector is usually just for extra CPU power (exceptions do apply).
    Just some nerd from 'Straya

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    Quote Originally Posted by ehume View Post
    But isn't the four-pin connector used for the PCIe plane?
    No. Not at all. Not sure who is spreading that rumor. If PCIe needs more power due to too many slots (like a cryptocurrency miner), then they would have PCIe six pin connectors on the board.

    You're not the first person I've heard claim that the additional 4-pin is for PCIe. That's wrong information and I'd like to know where it's coming from so I can confront them.

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    Yeah Plenty fine with the 8 pin EPS. It Don't even get close what use to get pulled out of them regularly. Yall correct again with the Optional extra Pcie power too and SLI...the evga board has that and some others.
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    Quote Originally Posted by ehume View Post
    But isn't the four-pin connector used for the PCIe plane?
    As the others said, no; that additional power connector is for the CPU and pretty much only "needed" in XOC circumstances. Otherwise it's pretty useless, even for the R7 1800X at it's highest liquid cooled capabilities.



    For suplemental PCI-e power board makers use additional 6pin PCI-e power connectors these days. Though board vendors in the past have used 4 pin molex or SATA connectors. The later was mostly just Gigabyte but both offerings had the same issue of only adding 1 additional 12v connection to the circuit so it didn't help much.

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