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Old September 28, 2011, 11:44 AM
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Default GTX 590 vs HD 6990 and explanation of 4-way SLI vs 3-way SLI

This is a question from MyToghrul:

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Hello.. I just want to ask something?? my motherboard is g1.assassin.. and i want to buy graphic card.. Which one is good? GTX 590 or HD 6990?? And what does it means: 4way crossfire?? 3 way SLI??
Right now for those cards it pretty much comes down to which one you can find in stock! They are both very rare. They perform very similarly, but I think I would pick the GTX 590 due to its low noise levels.

As for 4-way vs 3-way CrossfireX and SLI, that just refers to how many graphics processing units you have in your system. Here are a few example to demonstrate:

2x GTX 580 - This is 2-way SLI because each GTX 580 has a single processor on it.
3x GTX 580 - This is 3-way SLI
4x GTX 580 *very few boards support this* - This is 4-way SLI

2x GTX 590 - This is 4-way SLI because each of these graphics cards has two processors on it! The advantage is that it's cheaper than 4x GTX 580s and takes up more space, but the disadvantage is that due to the power constraints of PCIe (and cooling constraints) they are not as fast as 4 GTX 580s.
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Old September 28, 2011, 12:44 PM
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The same thing is for HD 6990?
2x HD 6990 - This is 4 way?
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Old September 28, 2011, 12:52 PM
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Yes it is, the 6990 is a dual GPU card.
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Old September 29, 2011, 10:31 AM
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Linus, one more question =]] Can i make SLI between GTX-590 and GTX-580? Or I can make SLI between same model?
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Old September 29, 2011, 10:59 AM
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Unfortunately you can only set up SLI between cards with the same GPU configuration.

For example, you can configure 2x GTX 580 in SLI even if one of them is MSI and the other one is EVGA, but you cannot configure them in SLI if one is GTX 580 and one is GTX 570.

CrossfireX is a little bit more flexible. As long as they are built on the same architecture, they can run in CrossfireX. For example, a 6990 can run with a 6970 in 3-way CrossfireX, and a 6970 can run with a 6950 in 2-way CrossfireX.
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Old September 29, 2011, 11:17 AM
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Just to clarify, a 590 is 2@580, but you cannot add 1 @590 + 1@ 580 to make 3 way SLI?

Thanks.
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Old September 29, 2011, 11:25 AM
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That is unfortunately correct.

All dual GPU NVIDIA cards are only 4-way SLI compatible using another identical card.
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Old September 29, 2011, 11:47 AM
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Quote:
Originally Posted by Linus View Post
Unfortunately you can only set up SLI between cards with the same GPU configuration.

For example, you can configure 2x GTX 580 in SLI even if one of them is MSI and the other one is EVGA, but you cannot configure them in SLI if one is GTX 580 and one is GTX 570.

CrossfireX is a little bit more flexible. As long as they are built on the same architecture, they can run in CrossfireX. For example, a 6990 can run with a 6970 in 3-way CrossfireX, and a 6970 can run with a 6950 in 2-way CrossfireX.
But the 6970 will downclock to the 6950 specs, faster card will always clock to the slowest one, another thing to note with a Crossfire/SLI setup is you are limited to the lowest amount of ram on a card, so a 1gb 6950 and a 2gb 6950 will only use 1gb in Crossfire. SLI is the same.
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Old September 29, 2011, 11:54 AM
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Quote:
Originally Posted by Supergrover View Post
But the 6970 will downclock to the 6950 specs, faster card will always clock to the slowest one, another thing to note with a Crossfire/SLI setup is you are limited to the lowest amount of ram on a card, so a 1gb 6950 and a 2gb 6950 will only use 1gb in Crossfire. SLI is the same.
Another thing to note is that when you crossfire or sli you do not then total the two cards vRam and say thats how much you have. You only have as much video ram as the lowest card that you have. If you have say 2 580 1.5GB, that means each card has 1.5GB of memory it can use, but you now have two cards performing the graphics computations rather then one, resulting in increased performance.
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Old September 29, 2011, 12:01 PM
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Quote:
Originally Posted by Arinoth View Post
Another thing to note is that when you crossfire or sli you do not then total the two cards vRam and say thats how much you have. You only have as much video ram as the lowest card that you have. If you have say 2 580 1.5GB, that means each card has 1.5GB of memory it can use, but you now have two cards performing the graphics computations rather then one, resulting in increased performance.
Thanks Ari, I should have made that clear in my post.

And no Performance doesnt scale with more cards, so say a 580 = a performance value of 10
adding another will not = 20
adding 2x more 580 will not = 30
The "sweet spot" seams to be 2x setups.
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