Question about SLI compatibility with the ASUS SABERTOOTH 990FX R2.0.

[Loli_Master]

This is my current build,

Case: Thermaltake Chaser A41
cpu: AMD FX-8350
mb: Asus m5a97 R2.0
gpu: EVGA GTX 760 ACX Superclocked
ram: Kingston HyperX Fury 2x4GB
psu: Corsair cx600m
hdd: WD 1TB Blue
cpu cooler: 212 Evo

Now on to my question i'm looking to upgrade my case, psu, motherboard and gpu to the following components.

Case: Corsair Air 540
psu: Corsair RM850
mb: Asus Sabertooth 990FX R2.0
gpu: EVGA GTX 970 Superclocked 4GB I plan to SLI these cards.

The reasoning behind the two cards in sli is because my uncle gave me his old two monitors and i'm going to get a third to match them and run them in nvidia surround at a resolution of 5760x1080p. The monitors if you're curious are Acer H236HL.

Now my question may be a little weird but i was wondering if i could use the 1st PCIe slot and the 4th PCIe slot for my SLI configuration? My reasoning behind this decision is because the evga 970s i'm getting are the ACX 2.0 cooled cards that push hot air around in the case and i figure they need some air to breathe instead of being sandwiched together in a traditional SLI configuration. But on the ASUS website when looking at the specs of the motherboard the top most slot is PCIe 2.0 x16 and the bottom most or 4th slot runs at PCIe 2.0 x8, will this make a big difference in performance across the two cards? Or will it be a negligible difference and i'm just over thinking this whole thing?

Sorry if i got a little overzealous with the explanation of my issue this is my first post on a tech forum and i wanted to make sure i didn't confuse anyone.

If you made it through all that you deserve a cookie!!

 

[jossrik]

You only have a couple things to worry about in this setup, and the 16x Vs. 8x isn't one of them. 1st make sure you get exactly the same card, SLI only plays nice with two of the exact same card. Second is the length of the SLI bridge. If it's long enough it should work in whatever slots you use. Don't take this as gospel, I haven't played with SLI in a long time, and crossfire is very forgiving by comparison. Also, the cards run fairly cool to begin with and the aftermarket coolers are pretty good, so I wouldn't worry about the cards being one right on top of the other, if your case has good airflow you'll be all right.

 

[Loli_Master]

You only have a couple things to worry about in this setup, and the 16x Vs. 8x isn't one of them. 1st make sure you get exactly the same card, SLI only plays nice with two of the exact same card. Second is the length of the SLI bridge. If it's long enough it should work in whatever slots you use. Don't take this as gospel, I haven't played with SLI in a long time, and crossfire is very forgiving by comparison.

I was aware that that you need two of the exact same card for SLI to work properly or at all. And on the topic of an SLI bridge that is the appropriate length i was looking at these two sli bridges.

http://www.amazon.com/gp/product/B0025VT6LQ/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A2H3QE25AGJEMY or
http://www.amazon.com/EVGA-Bridge-3-Way-Graphics-100-3W-0031-LR/dp/B00F93S5C8/ref=pd_cp_pc_3

i'm inclined to go with the second one because i'm going to be honest i love having all of my components match in one way or another.

 

[jossrik]

With the three way I'd be worried about the cards being 1st and 3rd positions. It shouldn't matter, but I've never built a three way SLI or a two way with a three way bridge. Have to wait for some one who knows more about NVidia bridges than I do.

 

[bignastyid]

For SLI on that board the only PCI-e slots you can use are pci-e slots 1 and 4(light tan colored slots) both will run at 16x unless you have a card plugged into the bottom pci-e slot(brown) then the 1st pci-e slot runs at 16x and the other 2 run at 8x. The board will come with an SLI bridge. For SLI the cards do not have to be identical they simply need to use the same gpu and have the same amount of vram. I would not suggest getting the RM850, while it's not a horrible psu it has issues and you can get better units for the same price or less.
http://pcpartpicker.com/part/evga-power-supply-220g20850xr
http://pcpartpicker.com/part/xfx-power-supply-p1850bbefx

 

[Loli_Master]

For SLI on that board the only PCI-e slots you can use are pci-e slots 1 and 4(light tan colored slots) both will run at 16x unless you have a card plugged into the bottom pci-e slot(brown) then the 1st pci-e slot runs at 16x and the other 2 run at 8x. The board will come with an SLI bridge. For SLI the cards do not have to be identical they simply need to use the same gpu and have the same amount of vram. I would not suggest getting the RM850, while it's not a horrible psu it has issues and you can get better units for the same price or less.
http://pcpartpicker.com/part/evga-power-supply-220g20850xr
http://pcpartpicker.com/part/xfx-power-supply-p1850bbefx

So what you're saying is that unless i go with a triple SLI configuration i can't space out the cards and use the top tan lane and the bottom brown lane in a normal 2 way SLI? Does the bottom brown lane only run at 8x if the system detects two other GPUs? If that's the case do you feel like the corsair air 540 case with 2 ACX 2.0 cooled EVGA GTX 970s will be okay temperature wise in an SLI configuration being that close together seeing as how they are double thick cards, and exhaust their heat out into the case? I'm sorry for asking so many questions btw.

 

[bignastyid]

I run 2 GTX 770 windforce cards in SLI and have them 2 slots apart(same spacing as yours would be) and they run just fine. With that case I would add another 140mm fan to the top as exhaust. The bottom brown slot will always run at 8x when its used. It maybe possible to run 2 way SLI in the top and bottom slot but I don't think there is an SLI bridge long enough so you'll almost have to use the 3-way bridge(never tried it but don't see any reason why it wouldn't work). The problem is the slots are PCI-e 2.0 and running a 970 in an 8x slot maybe a small bottleneck.

 

[Loli_Master]

I run 2 GTX 770 windforce cards in SLI and have them 2 slots apart(same spacing as yours would be) and they run just fine. With that case I would add another 140mm fan to the top as exhaust. The bottom brown slot will always run at 8x when its used. It maybe possible to run 2 way SLI in the top and bottom slot but I don't think there is an SLI bridge long enough so you'll almost have to use the 3-way bridge(never tried it but don't see any reason why it wouldn't work). The problem is the slots are PCI-e 2.0 and running a 970 in an 8x slot maybe a small bottleneck.

You and jossrik have been a huge help! Thanks a lot and i've decided to just use the two tan slots and i'm going to do what you've suggested and add another exhaust fan to the top of the case, to help get the hot air exhausted from the ACX cooled 970s out of the case instead of it swirling around in there.