Two GPUs in SLI in PCI-e x8 slots

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Pauuuuulix

Pauuuuulix

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Jun 19, 2014
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If i have a PCI Express x16 slot running at x16 and a PCI Express x16 slot, running at x8 and i want to have to gtx 780 SLI then how much does it affect the performance? And if I have 2x PCI Express x16 slots running at x8 and gtx 780 sli on them then how much does it affect the performance? Do they both run at 50% of their power?
 
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Hi pauuuulix,

running 780s in sli on pcie 3.0 8x and 8x, which is the only way it would run on the current z77,87,97 chipset should not make much of a difference in comparison to running 16x on x79 or using a PLX multiplier chip. Both 780s are running full speed...at least if the software supports sli.
Most the of the bottleneck (if I may use the word) is on the actual graphic processing on the GPU; at least with the current generation software. Maybe, in the future, when the PCIe 3.0 bus is saturated with the traffic running watch dogs 3.0 or cod: demons ... 780 sli is still sweet as pie.

Cheers and enjoy.
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sourodip

sourodip

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Jul 9, 2011
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In practical a 3.0 x16 slot is 0-3% faster than the 2.0. I assume you have the 2.0. It would work. You can SLI two 780's in x8/x8 mode, x4/x16 mode is much slower.What mobo and PSU do u have?Are u gaming on two monitors?
 
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kalijaga

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Nov 5, 2012
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Hi pauuuulix,

running 780s in sli on pcie 3.0 8x and 8x, which is the only way it would run on the current z77,87,97 chipset should not make much of a difference in comparison to running 16x on x79 or using a PLX multiplier chip. Both 780s are running full speed...at least if the software supports sli.
Most the of the bottleneck (if I may use the word) is on the actual graphic processing on the GPU; at least with the current generation software. Maybe, in the future, when the PCIe 3.0 bus is saturated with the traffic running watch dogs 3.0 or cod: demons ... 780 sli is still sweet as pie.

Cheers and enjoy.
 
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Pauuuuulix

Pauuuuulix

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Jun 19, 2014
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I have GA-Z97X-Gaming 3 Mobo(PCI-E 3.0) and Enermax ATX 2.3 Revolution X't 730W PSU. And i've heard that PCI-E 3.0 has 2x faster than 2.0. So if i have two 780s both in 8x slots they will run as fast as in 16x slots?
 
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ubercake

ubercake

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Oct 28, 2009
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Yes. Two 8x PCIe 3.0 slots offer the same bandwidth as two 16x PCIe 2.0 slots.

 
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kalijaga

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Nov 5, 2012
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With the current highest end single and dual GPU cards, the difference between x8 vs x16 at PCIE 3.0 will be negligible. Maybe later when we are running fully at 4k and above, there will be a difference
Yes, I accept the variability of VRAM limitations, CPU speed and threads, RAM usage in certain games but at the moment I feel 8GB/s @8.0 is enough to sustain our current GPU performance.



 
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