Problem Connecting More Gpus To Psu

Discussion in 'Rigs' started by gstn, Jul 23, 2017.

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  1. gstn

    gstn New Member

    Jul 23, 2017
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    Czech Republic
    Hi,

    i recently created my first rig setup :

    MB : Asus Z270-A Pro
    CPU : Celeron G3900
    4GB RAM
    120gb Corsair SSD

    PSU :850w Fortron (FSP) Hydro G
    GPU : 4x MSI GTX 1070 Gaming X

    First i connected only 2 GPUs because i was waiting for risers ... Configured the system optimized gpus ...

    My problem is that the PSU has 6x 6+2 pin output (3x2(6+2)) and the GPUS need 8+6 pin so at the moment i can run only 3 cards . I was trying to run 3-4 GPU just with 8 pins but that doesnt worked. Can i create another 8+6 pin from other (Sata,molex ports ? ) with adapters ? the whole system is currently consuming about 540w (with 3 cards) so there is plenty left for the 4 card.

    Thanks
     
  2. Johnshpon3

    Johnshpon3 Member

    Dec 25, 2015
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    Male
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    Slovenia
    When you use GPU's for mining they are working at 100% 24/7/365. Power they drain from PSU is more or less over the specified ammount. For example my Nano R9 is specified for max. power 175W but when mining it uses 200-215W. So your 150W should take with little reservation and maybe count it about 170-180W during mining.
    I would not recommend using another ports like SATA or Molex for additional power connection. They are just not make for such high power consumption. The best case woul be that it won't work, the worst you will burn that ports or whole PSU.
    I would buy another PSU, connect it in parallel with old one and use additional 8 pin rails. CAUTION: you need to be absolute sure what are you doing!!! (ask uncle Google how to do it)
    Another solution is to buy new PSU with enough 8 pin rails - most recommened if you are not skilled in electronics.
     
  3. gstn

    gstn New Member

    Jul 23, 2017
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    But my PSU has 6x8pins. GTX 1070 series has about 3/10 cards that have 8+6pin. Most of them have only 8pin connection. I want to use the 8 pin connectors directly from GPU ports on PSU. And the additional 6 pin from Y 2xSata to 6 pin. Most of the power should be from the 8 pin. The power consumption meter is showing 540w at the moment.
     
  4. Johnshpon3

    Johnshpon3 Member

    Dec 25, 2015
    210
    86
    Male
    Telecommunications
    Slovenia
    Problem is that SATA and Molex rails are not capable to provide enough power for missing PCIe rails even if your total power consumption not meet the maximum power of your PSU. You can not say where most power will come from. Parallel connection of power rails wil suck exactly half of current from each rail. Let say that your card need 200W. Half of wattage (8.33A) will drain from PCIe power connector what is OK but another half will drain from Molex or SATA what could be over maximum for them and Over Current Protection will be tripted.
    But you can allways try. Sometimes odd connections works. Let us know.

    P.S. Max wattage for 6 pin PCIe is 75W and 8 pin PCIe is 150W. Some better PSU's can exceed this parameters slightly without causing damage to PSU or trip OVC to early.
     
  5. gstn

    gstn New Member

    Jul 23, 2017
    3
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    Male
    Czech Republic
    Well, i connected the GPUs and theyre working fine (for now :D) .... but i will buy +1 PSU and connect a 5 gpu.. dont wanna risk. Thanks for all advices. At least we know there is a cheap temporary solution.
     

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