Hi. I`m building my new rig using Rampage V Edition 10 and i7 6850K. I also planning to use 2X Intel 750 series 400gb on Raid 0.
I just now purchase GTX Titan x pascal on Nvidia website for only USD 1200 😄 . I`m gonna do Titan 2way SLI on my new rig.
I have 2 cards of GTX 680 from my old rig and I`m gonna use one of them as a physx card.

Now I face a problem. RVE10 (Rampage V Edition 10) is only have 40 PCIE lanes.
If I do native 16X SLI with 2 Titans it takes 2X16 Lanes = 32 PCIE lanes?
if I were to use M.2 and U.2 it takes 8 Pcie lanes, am I correct?

In Asus RVE manual it mention that The PCIEX8_4 slot shares bandwidth with M.2 and U.2.
Manual also mention The PCIEX4_1 slot shares bandwidth with front USB3_34 ports and back USB3.1_EC1_EA2 ports.
If a X2 device is connected to the PCIEx4_1 slot, the front USB3_34 ports will be disabled.
If a X4 or higher device is connected to the PCIEx4_1 slot, both front USB3_34 and back USB3.1_EC1_EA2 ports will be disabled.

If I add GTX 680 card as a physx card on PCIE X8-2 will it use 8 PCIE lanes?I so can we make it to use one PCIE lane or 2?

If my understanding is right-
Titan X SLI PCIEX16_1 and PCIE X16_3 = 32 PCIE lanes.
PCIE X4_1 is for USB = 4 PCIE lanes.
GTX 680 physx = 8 PCIE lanes.
m.2 + U.2 use PCIE X8_4 = 8 PCIE lanes.

If my calculation is correct. There is a possibility that i`m totally wrong and I wish I`am, then it might need 52 PCIE lanes to work.
If i run Titans in 8X if it gonna be lose of performance? I really cant figure it out and i feel awful :(.
I`ll add 2 photos of what I download from Asus RVE10 manual.

Little help is much appreciated.