Connect Thunderboltex 3 card without sacrificing speed of other lanes?

[ayylmao78]

I am in a bit of a pickle here. I got a thunderbolt extension card that came with my x99 Deluxe II motherboard but I cannot seem to figure out an efficient way to connect it. I will try my best to explain the situation:
I got a GTX 1080 connected to my PCIE-1 slot and since the card is big, it obstructs the PCIE-2 slot so I cannot use that. PCIE-3 slot shares bandwidth with my NVME SSD so I obviously would not want to connect it there. Only 2 slots remain: PCIE-4 and PCIE-5. If I connect the card to PCIE-4, my GPU no longer runs at x16 and is limited to X8. PCIE-5 should save the day, right? Not quite... I cannot select PCIE-5 in my UEFI settings for the thunderbolt. I can only select 1,2,3 or 4 but not 5.

my CPU is a 28 laner i7 5820k

any suggestions would be greatly appreciated...

PS: I know that if my card runs at 8x, it doesn't affect the performance that much but there is still an ever slight difference between x8 and x16 so I'd like to avoid running my GPU at x8 at all costs

[xeromist]

If you won't move your GPU then use a PCIE extender ribbon to access the slot under it.

[ayylmao78]

If you won't move your GPU then use a PCIE extender ribbon to access the slot under it.

That is actually a good idea. Is there any way to figure out if my slot 2 works on at least x4 speeds? (x4 is required for thunderbolt). I also hope that it doesn't share bandwidth with slot 3 or slot 1 cuz that would be useless then

[xeromist]

A lot of times that is in the manual so I'd check there. It will say how populating different slots changes their bandwidth. If it's not there then I don't know. You might have to get creative with diagnostic tools or test it with benchmarks. Perhaps someone has already posted that online so I'd do some Google searching too.

The good news is that extender cables aren't overly expensive and it's useful to have one around if you work on your own machines. So even if you use it for a while and put it in a drawer you might want it again in the future.