Please help me understand sli

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g335

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Oct 14, 2008
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Hello

I asked about SLI before but I don't understand.

When is it needed?

I read that 2 GTX970's are better than 1 GTX 980.
How?

I thought that even with two gpu's that the game or programs only reads the gpu ram from one card.
 
Solution
guanyu210379
A single GTX970 is only 10-15% slower than a GTX980
2 GTX970s on SLI can run up to around 80% faster than a single GTX970.
Thus, 2 GTX970s on SLI is faster than a single GTX980...as long as you do not hit the 3.5GB VRAM limit...
A single GTX980 could beat GTX970s in SLI if you uses VRAM above 3.5GB.

Do not forget to pay attention to SLI operation mode, the result varies from games to games.
Some games have even problems with SLI.
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Grimwinder

Grimwinder

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Jul 2, 2014
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That's true on the vram, however you would have 2 GPUs sharing the workload. The amount SLI helps really depends on the game you are running and at what settings. On the whole, 2x970s in SLI will be better than one 980, but whether or not it's worth it depends on what you are trying to play and, again, at what settings.
 
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drixkarasu

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When 2 cards are in SLI the VRAM content is mirrored in both cards, so you have the same VRAM as with a single card, but you have 2 GPU rendering frames which is much faster than having a single one doing it. 2 970 in SLI should be about 80-90% faster than a single 970, therefore also faster than a 980.
 
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bootcher

bootcher

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Feb 22, 2013
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in SLI or Crossfire two cards take turns in rendering 1 frame. So to simplify the explanation, instead of 1 card doing all the work, two cards do each 50%. This (usually) enables much higher performance than one card of the same type. Because the two cards have to know which frame they are rendering to make sure everything works, both have to keep copies of eachother in their memory/vram. This is why in SLI/crossfire your amount of vram does not double, it stays the same (or it is limited by the lowest amount of available vram in one of the cards).
In short your GPU power increases but your amount of vram stays the same.
 
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guanyu210379

guanyu210379

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Mar 30, 2007
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A single GTX970 is only 10-15% slower than a GTX980
2 GTX970s on SLI can run up to around 80% faster than a single GTX970.
Thus, 2 GTX970s on SLI is faster than a single GTX980...as long as you do not hit the 3.5GB VRAM limit...
A single GTX980 could beat GTX970s in SLI if you uses VRAM above 3.5GB.

Do not forget to pay attention to SLI operation mode, the result varies from games to games.
Some games have even problems with SLI.
 
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