GTX580 and 16x vs 8x 2.0 PCI-E Slot

[Bladespirits]

Alright so I read this http://www.techpowerup.com/reviews/NVIDIA/GTX_480_PCI-Express_Scaling/

And I was wondering if this will still hold true for the 580. And also one question I had from the above article is how much/any does SLi effect the overall performance of having 2 cards in 8x versus 2 cards in 16x? I ask because I'm looking at getting a P67 board and at first will only have a single 580, but I run 2560x1600 resolution so I know I'm going to need to throw a second one in there 2-3 years down the road to keep my resolution maxed.

Oh and another question.. how well do dual GPU cards perform in an 8x slot? I have no plans of getting one, but am curious.

 

[Tamz_msc]

The difference would be barely noticeable.

 

[Maziar]

Right^
The difference between dual x16 and x8 isn't much.(The most FPS difference is at resolutions like 2560x1600 which is still nothing much,maybe 5-10% max)So don't worry about the performance loss.

 

[Bladespirits]

Is there nobody out there that's actually tested this though with a 580 let alone 2 580's in SLi? Was looking back at older Tom's Hardware articles and found one for PCI-E 1.0 and the 8800 needed 16x to make full use of its card. And with PCI-E 3.0 right around the bend I can't imagine we're not getting close to some threshold again.

 

[Snipergod87]

There probably are people who tested it. But you may see a 1-2% decrease as opposed to 16x 16x, not really noticable at all.

 

[17seconds]

This is a good series of articles on the subject from Hardocp.com. They claim there is no noticable difference using SLI GTX480's in X16 vs. X8, or even vs. x4 slots.
http://hardocp.com/article/2010/08/16/sli_cfx_pcie_bandwidth_perf_x16x16_vs_x16x8/
http://hardocp.com/article/2010/08/23/gtx_480_sli_pcie_bandwidth_perf_x16x16_vs_x8x8/
http://www.hardocp.com/article/2010/08/25/gtx_480_sli_pcie_bandwidth_perf_x16x16_vs_x4x4/

 

[Bladespirits]

Thanks matto17secs for finding that. Was hoping for some 580 testing (which obviously hasn't been done since it hasn't been an issue since X58 came out till now P67 coming out) but seeing how even running 2560x1600 resolution on 4x lanes isn't bottlenecking I feel comfortable throwing 2x 580's on 8x lanes.

 

[Bladespirits]

Best answer selected by Bladespirits.

 

[Bladespirits]

I never even thought of factoring in how cards SLi/Xfire performance was effected by the motherboard.

Any small loss in 8x seems more then made up for with improvements to the scaling

http://www.legitreviews.com/article/1500/8/