Motherboard for i7 6800K and 4 GTX 1080 ti

[wattskaggle]

I am currently using an i7 6800K (socket LGA2011-3) with an Asus X-99 E WS motherboard with a single NVIDIA GTX 1080 Ti card. I want to upgrade and install additional 3 GTX 1080 Ti GPUs so that rig has a total of 4 GPUs. I want to use GTX 1080 Ti only.
I do not want to use any riser cables as I have heard it causes GPU performance degradation. Instead I want to fit all the 4 cards directly into the PCI-E slots. The challenge is that a single GTX 1080 Ti takes up the space for 2 slots.
Can you please suggest a motherboard with sufficient physical spacing between PCI-E slots so that one motherboard can fit 4 GTX 1080 Ti cards without any riser cables?

 

[animemangamer]

https://www.asus.com/us/Motherboards/ROG-RAMPAGE-V-EDITION-10/

Why can't you just use the same motherboard? it supports 4-way SLI:

 

[wattskaggle]

https://www.asus.com/us/Motherboards/ROG-RAMPAGE-V-EDITION-10/

Why can't you just use the same motherboard? it supports 4-way SLI:

See attached url of my rig. Looks like X-99 E WS can take 3 1080Ti cards, not 4. Looks like we need a motherboard with 6 PCI-e slots not 4.
rig internal

 

[animemangamer]

See attached url of my rig. Looks like X-99 E WS can take 3 1080Ti cards, not 4. Looks like we need a motherboard with 6 PCI-e slots not 4.

The problem is you're STRIX 1080 Ti has a huge heatsink/cooler that it exceeds over to the next pci slot. Not to mention, you also need to change your case as you can clearly see the PSU will be on the way (the PSU that you need to upgrade as well to power all these hungry cards)

For comparison here is an FE 1080Ti:

EVGA 1080 Ti:

Gigabyte 1080 Ti:

You can get 1080 Ti's like those that don't run over the next PCI slot or what you can also do is change their cooling method into waterblocks which what most do with SLI (because the cards are so close to each other that there's barely any airflow in between)