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How to calculate total current(A) of a PSU for a GPU

Hi everyone.

I saw a 600W PSU with two +12V rails each on 18A. Will this be able to power a GTX660Ti or a GTX570.

Do you sum the current?
In this case it will be 36A when considering the minimum GPU requiments:
GTX660Ti needs 450W rated 24A
GTX570 needs 550W rated 34A

Thanks a Lot for your Intelligence
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  1. Yes a 600 Watt PSU as long as it is listed as a "Quality" PSU not a Door stop. Brand/model please.

    Total system power for a 570 is around 446W running furmark (approx 361 W running cryis).
    Ref: http://www.anandtech.com/show/4051/nvidias-geforce-gtx-570-filling-in-the-gaps/15

    And an excellent PSU would be: http://www.newegg.com/Product/Product.aspx?Item=N82E16817139005
  2. Guys, what about the ohms or current(A). How much will it be if you have two 600W with two +12v rails rated at 22A. And there is two 6pin connectors.
    Will it be 22*2 = 42A
  3. Best answer
    Dumisani said:
    Hi everyone.

    I saw a 600W PSU with two +12V rails each on 18A. Will this be able to power a GTX660Ti or a GTX570.

    Do you sum the current?
    In this case it will be 36A when considering the minimum GPU requiments:
    GTX660Ti needs 450W rated 24A
    GTX570 needs 550W rated 34A

    Thanks a Lot for your Intelligence


    450 and 550 are total system watts not gpu watts. And remember wattage is equal to Volts X Amps or Amps^2 X Resistance.
  4. Best answer selected by Dumisani.
  5. I see the 600W >550W is enough but the GPU needs 34A, this PSU has only two 22A rails. And it has two 6pin connectors
  6. as far as the first set of specs you listed with two 12 volts rails listed @ 18 amps each:
    18*2=36amps*12volts=432watts/600watts=72% of total wattage.

    AFAIK any PSU that cannot deliver 80%+ of total wattage on the 12 volt rail is not desirable since most computers now a days draw most of its power from the 12 volt rail.
  7. As looniam has pointed out, the 12v rail is the most cruicial part of a PSU, this is where significant power draw is.
  8. Anonymous said:
    as far as the first set of specs you listed with two 12 volts rails listed @ 18 amps each:
    18*2=36amps*12volts=432watts/600watts=72% of total wattage.

    AFAIK any PSU that cannot deliver 80%+ of total wattage on the 12 volt rail is not desirable since most computers now a days draw most of its power from the 12 volt rail.



    Thanks a Lot. This makes sense, I understand now.
    Does this mean that even a 500W rated @ 22A with two +12V rails, & 80%+totalWattage can power the GTX570 using a one 6pin connector plus a Molex convertor for the second 6pin required by the Card.
  9. easiest and simplest way to choose a power supply to power ur gtx570

    1st, look for these reliable brands > corsair, antec, seasonic, pc power & cooling, XFX etc...

    2nd, determine which has the least amount of pcie connectors required for ur gtx570 (in this case 1 6pin and 1 8pin)

    3rd, choose one that u think is most affordable

    problem solved

    no need to screw up urself by making things complicated eg: calculate how many watt, volt etc, purchace any molex cables (u shouldnt operate ur psu above its spec anyway)
  10. lengcaifai said:
    easiest and simplest way to choose a power supply to power ur gtx570

    1st, look for these reliable brands > corsair, antec, seasonic, pc power & cooling, XFX

    2nd, determine which has the least amount of pcie connectors required for ur gtx570 (in this case 1 6pin and 1 8pin)

    3rd, choose one that u think is most affordable

    problem solved


    Thanks I am going for a 650W Antec PSU.
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