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Amp requirements in SLI/Cross-Fire

post #1 of 3
Thread Starter 
I was reading this site (http://forum-en.msi.com/index.php?topic=104805.0;wap2), assuming it's numbers are accurate, and I'm wondering how SLI Amp calculations work. Don`t we just double the number of a single card to see the amp requirements in SLI? How come the 590 in SLI is less the double the amps of a single 590? Shouldn't it be twice the amps?

Quote:
nVidia

GeForce GTX 590 in SLi - 78A and a 1000W PSU minimum
GeForce GTX 590 - 46A and a 700W PSU minimum

GeForce GTX 580 - 40A and a 600W PSU minimum
GeForce GTX 570 - 35A and a 550W PSU minimum
GeForce GTX 560 Ti in SLi - 42A and a 700W PSU minimum
GeForce GTX 560 Ti - 31A and a 500W PSU minimum
GeForce GTX 550 Ti - 28A and a 450W PSU minimum
GeForce GTX 470 and 480 in SLi - 55-60A and a 850W PSU minimum
GeForce GTX 480 - 42A and a 600W PSU minimum
GeForce GTX 470 - 38A and a 550W PSU minimum
GeForce GTX 465 in SLi - 46A and a 700W PSU minimum
GeForce GTX 465 - 30A and a 500W PSU minimum
GeForce GTX 460 in SLi - 42A and a 650W PSU minimum
GeForce GTX 460 - 26A and a 450W PSU minimum
GeForce GTS 450 in SLi - 35A and a 600W PSU minimum
GeForce GTS 450 - 24A and a 450W PSU minimum


more listed in link........
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post #2 of 3
It's because the power supply also powers the rest of the system, not just the cards. Adding another card uses less power than just doubling the usage of a single card.

The ratings take into account powering the motherboard and other peripherals too. Let's say, hypothetically, that other system components use 10A and a single card uses 30A. Two cards + the motherboard = 70A, when compared to one card which would be 40A. It's less than double. The same principle applies here. You really think a single GPU would use 700W?
Edited by jNSK - 4/26/11 at 4:00am
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post #3 of 3
Thread Starter 
Oh, I thought it just meant how much Amps each card takes separately, and the wattage part was for the whole system. Never thought the amps part included the whole system.

Thanks for clearing this up.
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