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

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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

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

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a b U Graphics card

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.

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
Anonymous
a c 117 U Graphics card

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.

As looniam has pointed out, the 12v rail is the most cruicial part of a PSU, this is where significant power draw is.

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.

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)

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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