Tri-SLI/CF on x8/x8/x4?

[Blackout621]

Hey guys,

I purchased the Asus P8Z68 a few days ago on Newegg.
So after hearing that my current motherboard wouldn't support 3-way SLI, I went to Newegg to RMA. However to my discontent, they're charging $35 for a restocking fee PLUS I have to pay shipping! You may think "you can spend $3200 on a computer but not be okay with a $40 loss?" but I'm weird about my money. I can splurge some places, but be a total tightwad in others. Anyway while my motherboard DOES have three PCI slots, the third one runs at x4 only. I know x8 is really ideal, but I found this:
http://www.techpowerup.com/reviews/NVIDIA/GTX_480_PCI-Express_Scaling/7.html
It seems the gap gets smaller and smaller between x16 and x4 the higher resolution you play at.
I know the 480 isn't anywhere near a 780 or 7970, but with tri-sli/CF of one of the cards mentioned, am I going to see micro-stuttering and a massive bottleneck running the third card at x4? Keep in mind I WILL be playing at a resolution of 5760 x 1080. Thanks for your patience and on-going support. Not only do you guys give great advice, but I learn along the way!
I can handle a 10 FPS drop if that's the case, but really no more than that. Would I be better off getting an AsRock board, accepting a $40 loss, and having a GEN3 motherboard suited for 3-way graphics?

 

[a4mula]

You won't see micro-stuttering as the 3rd card disrupts the ability for AFR to fall out of sequence. With that being said there's really no good data that shows what type of bottlenecks are found in today's gpus at Eyefinity resolutions while using x8/x8, let alone an x4 slot.

According to this review http://www.hardocp.com/article/2010/08/23/gtx_480_sli_pcie_bandwidth_perf_x16x16_vs_x8x8/3 the bottleneck of x8/x8 increases the higher the resolution becomes which is intuitively obvious. The more throughput the cards are having to output the more the bottleneck becomes.

I'd hate to imagine what kind of losses you'd see with a modern card like the 7970 but at your resolutions I'd say they'd be more than just blips on a benchmark.

This is something I fought with while considering my new Eyefinity build which would have been 3x1920x1200 for a 3600x1920 portrait. Ultimately I decided that the only way to avoid this would be to go with a NF200 Z68 board, or (and what I have decided to do) go with X79.

At this point in your purchase cycle I'd say you have a tough decision to make. You can roll the dice and hope that x8/x8/x4 will be satisfactory or you can RMA and go with a board like the Z68 Extreme7 which is a x16/x16/x8 solution. I'd recommend the second just because after spending the money it takes to build one of these rigs I'd hate to think that my performance was being affected by something as simple as a pci-e lane.

Best of luck either way, and if you don't mind keeping us up to date I'd be extremely interested in seeing how this turns out for you.

 

[k1114]

http://www.tomshardware.com/reviews/p67-gaming-3-way-sli-three-card-crossfire,2910-16.html This may be of interest although it only goes up to 2560x1600. Worst case was 20fps drop but most games were hardly affected. It does become more apparent the higher res and more aa though.

 

[Blackout621]

You won't see micro-stuttering as the 3rd card disrupts the ability for AFR to fall out of sequence. With that being said there's really no good data that shows what type of bottlenecks are found in today's gpus at Eyefinity resolutions while using x8/x8, let alone an x4 slot.

According to this review http://www.hardocp.com/article/2010/08/23/gtx_480_sli_pcie_bandwidth_perf_x16x16_vs_x8x8/3 the bottleneck of x8/x8 increases the higher the resolution becomes which is intuitively obvious. The more throughput the cards are having to output the more the bottleneck becomes.

I'd hate to imagine what kind of losses you'd see with a modern card like the 7970 but at your resolutions I'd say they'd be more than just blips on a benchmark.

This is something I fought with while considering my new Eyefinity build which would have been 3x1920x1200 for a 3600x1920 portrait. Ultimately I decided that the only way to avoid this would be to go with a NF200 Z68 board, or (and what I have decided to do) go with X79.

At this point in your purchase cycle I'd say you have a tough decision to make. You can roll the dice and hope that x8/x8/x4 will be satisfactory or you can RMA and go with a board like the Z68 Extreme7 which is a x16/x16/x8 solution. I'd recommend the second just because after spending the money it takes to build one of these rigs I'd hate to think that my performance was being affected by something as simple as a pci-e lane.

Best of luck either way, and if you don't mind keeping us up to date I'd be extremely interested in seeing how this turns out for you.

Thanks for the fast and helpful answer! I think what I'm going to do is sell the motherboard on OCN and hopefully get $200ish. I think losing a little money is worth getting a suitable motherboard for 3-way SLI/Crossfire. I will certainly let you know how it all turns out. I'm not building until whenever Kepler comes out, though, so keep that in mind. Thanks again!

 

[Blackout621]

Best answer selected by blackout621.