+1 With most of the non-FE 1080 Ti cards now approaching 3 slots in width, I strongly suspect that your top GPU is overheating because its three fans cannot freely blow its hot air out due to the bottom GPU's backplate pressing up so close to the top GPU's fans. So for all these Gigabyte, Asus, MSI, and other non-FE 1080 Ti's, you really need at least 4 slots of separation between the top and bottom GPU.
Another option would be to keep your two fat (and too fat :-) Aorus GPUs together and use them in SLI on a different motherboard that has 4 slots of separation in the x8/x8 slots. But then you have to buy another motherboard. Many mobos have 3 slots of separation (e.g. with two x1 slots in between), but there are various mobos with 4 slots of separation.
I have two MSI 1080 Ti Gaming X GPUs that are also approaching 3 slots in width. But with 4 slots of PCIe separation, there is almost one and a half slots of separation between the top GPU's fans and the bottom GPUs backplate and both GPUs have similar temps that never exceed 65 or 70 degrees-C.
I made a similar inquiry on this build:
and that person replied "Never reached 70C° on the main card after hours of intense gaming. " His two GPUs are almost touching each other, so I am not sure that I believe both his GPUs "never reach 70 degrees-C".
On that other Evolv build, I did not believe his comment of "Never reached 70C°" on both of his GPUs, but I was not going to disagree and debate with him.
Both 1080 Ti GPUs still look very nice stacked with an extra slot of spacing in between them. Those downward-pointing GPU fans are there for a very important reason :) With most GPUs, the top of the GPU, with or without a backplate, does not matter for ventilation since only a slight bit of warmth is released from the top, but the GPU's heatsink is entirely dependent upon its bottom-facing fans for cooling. So if you mash two GPUs together with no separation, the top GPU heats up while the bottom GPU stays cool.
If Nvidia's next GTX 1180 cards run even hotter, it will get to a point where you are required to use a mobo with 4 slots of separation for dual-GPU SLI, or else you have to set up a custom water loop with slim water blocks on the GPUs.
Buying another Z270 mobo with 4-slots of x8 PCIe separation is MUCH cheaper than buying a new 2011-v3 CPU and mobo. This is how people justify extra purchases for their PC-building passion: (1) I need a new 2011-v3 CPU and mobo to make better use of my Evolv and SLI 1080 Ti's; (2) Oh wait... now I have a spare Z270 mobo with an unused i7-7700K, so now I need a new PC case, power supply, and RAM to make use of my extra Z270 mobo. See how easy that was to drain your wallet? ;-)
I also don't think anyone notices any gaming difference between two LGA1151 x8/x8 SLI GPUs and two LGA2011 x16/x16 SLI GPUs. Even with two 1080 Ti's, I would not be surprised if the difference is only 1 or 2 FPS, or less.
Damn your girl knows how to game
+1 for all that power.
I have the Asus 1080Ti in SLI and they are also 1 1/2 wide. I have them in a Corsair Air 540 case with 3 fans in front with 2 of them connected to the fan headers on the cards blowing cool are on them. Top card peaks at arounf 72C and the bottom card stays 8C to 12C cooler. Ambient temps where I live are at 27C to 30C.
Thas also a hefty power supply. I have the 850W of the same PSU and max power draw at 99% load on both PSU come to around 630W peak.
I had tried the Evolv TG case and found the air flow restrictive. Its a beautiful case to be sure but I was not too satisfied wih it.
Hmm. Thanks for the heads up.