Rampage IV Gene Crossfire question

[Kevin Spring]

Per Asus's documentation and online chat support, they state that you can only run crossfire/sli in the 1st and 3rd pcie slots, which are physical and electrical pcie 3.0 16x slots. I'm wondering if I could run crossfire in the 1st and 4th slots (the 4th is a physical 16x but an electrical 8x) so that the 3rd slot remains open for a wifi card or usb 3.0 card (the board only has two on the rear io). My thinking is that pcie 3.0 8x shouldn't bottleneck crossfire at all, so I don't understand why I can't do this. My case does have a 5th expansion slot, so that isn't an issue either.

also, any thoughts on whether the Noctua NH-D15 would fit with this mobo? It will fit the case but what about obstructing ram slots or the 1st pcie slot?

 

[cin19]

Yes, you can use the 1st/ 4th for the dual GPUs, here is the review for x16/x16 vs x16/x8 performances. http://www.hardocp.com/article/2010/08/16/sli_cfx_pcie_bandwidth_perf_x16x16_vs_x16x8/4#.U5CTAHZ5Jc1

And the NH-D15 is too big, it does not fit because it will block the 1st pcie slot. Compatibility lists http://www.noctua.at/main.php?show=compatibility_gen&products_id=68&lng=en#LGA2011_Asus

If you like the Noctua brand, you can use the NH-D14 with LGA2011 Mounting-Kit and also insulate the fan clips using duct tape if they are close to the GPU. http://www.noctua.at/main.php?show=faqs_single&faqs_id=53&lng=en Compatibility lists http://www.noctua.at/main.php?show=compatibility_gen&products_id=34&lng=en#Asus

Or the H2O cooler.