780 wind force SLI PSU...

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amer1234

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May 12, 2013
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hello every one...

I have a question about how much PSU do i need for 2 780 SLI both at 16× ... i did some searching but they all say 850w would be enugh...

But if both the GPU's were in 16× PCIE will they consume more power ?

I mean will 860w be enaugh for a haswell CPU "4770K"

And 2× 780 Gigabyte windforce edition both at 16× PCIE

or should i get a 1200w ?

and thanks...
 
Solution
fudoka711


Yea, that can be pretty confusing. GPU manufacturers always state wattage on the...
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ingtar33

ingtar33

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Dec 17, 2012
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the windforce are 300W gps when overclocked... the haswell is a 230W cpu when overclocked that means your system will be something like a 850W system. I would get a 1000W gold rated psu, or a 1100W bronze. the people claiming 800W is enough are probably adding up the wattage and forgetting that you're overclocking and that psus don't deliver their claimed wattage but generally as much as only 80% of their claimed number, meaning you'd need a 1000W psu to produce 800W of power on a bronze psu.
 
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amer1234

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May 12, 2013
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10,510


Thanks for the reply ...

but in the Gigabyte site it says it's a 450w ... not 300w
http://www.gigabyte.com/products/product-page.aspx?pid=4621#ov
 
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fudoka711

fudoka711

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Apr 2, 2012
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Yea, that can be pretty confusing. GPU manufacturers always state wattage on the conservative side and pretty much always overstate how much wattage you actually need. Under where it talks about "450w cooling system", it also mentions that you should have a 600w psu. Ignore both numbers since you're asking us here. The 450w most likely refers to how many watts the cooling system can cool (aka the 3 fans and heatsink) and the 600w is the conservative number I was referring to. The actual wattage that the card will draw is much closer to the 300w that ingtar33 was talking about. Getting a 1000W 80 Plus Gold PSU is your best bet as your total system power draw will indeed be around 800-850w.
 
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ingtar33

ingtar33

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Dec 17, 2012
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bingo. gpu manufacturers don't know what crappy psu you might have. some psus are so poor they don't even deliver 1/2 their advertised power, so the gpu companies cover their backsides and suggest something in the range of a little more then x2 the max power draw of the gpu as the min psu needed for your system.

The 780 windforce is a little bit less then a 300W gpu when overclocked... i rounded up to 300W by 30-60W because i don't want to underestimate what your power draw is. The haswell when overclocked and under 100% load will draw a little less then 250W, which means if your system is under 100% load you'll probably draw around 750W-850W... a solid gold rated 1000W psu should cover your needs as your system will never be at 100% total load even when stress testing. To be a gold rated psu the psu needs to be 90% efficient, which means it will put out a consistent 900W under load, which will cover your whole system under a worst case scenario.

 
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