Guessing the extra lanes help, doubt you'd be able to run all of them at x16 though but SLI and Crossfire 3x might be achievable without having one of them running in 8x mode. (Of course SLI and Crossfire scaling at 3x or 4x GPU's is a bit of a problem.) Albeit aside from that I guess PCI-E SSD storage could benefit too. Not sure if there's much that actually maximize PCI-E 3.0 bandwidth availability even with the newer SSD's but I guess that's what the upcoming 3.1 version of it or what it was called will be improving on? (SATA4 would probably help too whenever that comes out specifically for high-speed storage units.)

Guessing the extra lanes help, doubt you'd be able to run all of them at x16 though but SLI and Crossfire 3x might be achievable without having one of them running in 8x mode. (Of course SLI and Crossfire scaling at 3x or 4x GPU's is a bit of a problem.) Albeit aside from that I guess PCI-E SSD storage could benefit too. Not sure if there's much that actually maximize PCI-E 3.0 bandwidth availability even with the newer SSD's but I guess that's what the upcoming 3.1 version of it or what it was called will be improving on? (SATA4 would probably help too whenever that comes out specifically for high-speed storage units.)

Scaling is just fine when a game is developed for it and not gimped out to please the masses of console purity.... I am not sure if these new motherboards are an example of what to expect in the multi-gpu realm of things, or if this is a "have to" by the manufacturers due to PCI-e limitations....? Meaning that they need to cram so many more options into it all dealing with PCI-e lanes, so more things need be changed/removed....

I'm pretty out of it when it comes down to actual hardware so I'm not too sure either, guessing stuff like HBM might benefit in particular as data is sent and received through the PCI-E bus although from what I've seen in some comparisons and tests GPU performance isn't really affected that much whether it's PCI-E 3.0 x16 or 3.0 x8 or even 2.0 on older motherboards. And for Crossfire and SLI they're probably going to be driver dependent for quite some time yet even with DX12 and Vulkan giving the developers more control (And ways to break things?) from what I've read scaling works reasonably well with dual GPU's as long as the game is multi-GPU compatible but at 3x and then 4x Crossfire or SLI it deteriorates somewhat, think Nvidia is even limiting Pascal to 2x SLI without a little update that can be requested to lift that. (Though perhaps they've gotten rid of that requirement by now.) And then there's Crossfire and SLI also differing a bit with SLI using that little bridge cable to deliver I think it was 1 GB/s and now it's 2 GB/s with that hi-speed bridge (Making what seems to be absolutely no difference at all in terms of GPU performance at least for current GPU models.) whereas AMD uses the PCI-E bridge directly (XDMA) and gets rid of the little bridge connector for it's newer GPU models and the bandwidth can be whatever the PCI-E bus max is which currently is at 32 GB/s with PCI-E 3.0 at 16x from what I found though well if 1 GB/s is enough for the newest Nvidia GPU's I'm guessing this makes little to no difference. (Importance being more about the driver and then how the actual game works plus current AFR scaling and micro-stutter issues.)

Vroom vroom.