Hello, 
 
My Evga GTX 970 SSC ACX2.0+ is not recognize at x16 , only x8. My second GTX 970 SSC ACX2.0 is recognize in 16X in the same motherboard same slot.
 
I've not noticed this issus before because the 2 cards have been used in sli with a i7 7800x who was only capable of x16 + x8. but now I have a i9 9820x who was capable of x16 / x16 and the car is still in x8.
 
Tested with:
evga x299 micro 2
i9 9820x
i7 7800x
 
also tested with:
Msi b450i gamings plus ac
ryzen 3 3100 
ryzen 3 1200af (970 only recognize at x4 with bios tweak, faulty cpu I think because same issus with the second 970)
 
Rampage 3 gene 
x5670
 
Maximus VIII hero 
i7 6700k
 
Do someone know something to solve that ? I think it was and issus in the graphic card it self
 

This is normal! Nothing wrong with your graphic card! When you have two same 970 SSC ACX2.0 GPU it will become x16 and x8 or if just one graphic card it will be at x16.
 
Please check in your manual book for X299 Micro ATX2 pages 11
 
On your motherboard see pic for number 11
 

 It same to my Z370 Classy do support both graphics x8 if I want one Graphic card then then it will become x16. Do not worry it no different speed really! It for share to other device on your motherboard! 
 
Have a look on my in NVIDIA inspector got my two GTX1080 Classy

 

according to x299 micro 2 data sheet the board is able to do x16 + x16 with a 44 pcie line cpu (like in my case).
 
the probleme is from my graphic card and not from my motherboard.
 
does a clean of full pcb can solve it ? or putting it in an oven 220°C 5Min ? 

vertex72
according to x299 micro 2 data sheet the board is able to do x16 + x16 with a 44 pcie line cpu (like in my case).
 
the probleme is from my graphic card and not from my motherboard.
 
does a clean of full pcb can solve it ? or putting it in an oven 220°C 5Min ? 

Run GPU-Z & test the PCIe status
 
Confirm your PCIe BIOS settings ... if set to Auto .. try setting to 3.0
 
anything in the x4 slot ?
 
how many M.2 devices ?
 
Manual page 22 PCIe lanes

pcie slot set at x16 and x16 3.0 , 1 nvme x4 in vme slot, nothing in pch x4.
to resume,
 
graphic card 1 : evga gtx 970 ssc acx2.0+
x16 3.0 in all slot in differents motherboard
 
graphic card 2 : evga gtx 970 ssc acx2.0+
x8 3.0 in all slot, test in different motherboard and still x8 

did you use the GPU-Z test ?  some cards only show PCIe 3.0 under load ... no idea why just remember reading it
 
Inspect your MB PCIe sockets with a light & magnification ... could be some sort of issue ?

Yes, bios set to 3.0, with gpu-z stress test gpu 1 is at x16 and gpu 2 at x8

Your video card comes with dual vbios. Does the secondary vbios also cause the same issue? If yes, you'll need to rma your card.

Ok i tested the second bios, stil x8, tomorrow i’ll clean the card with contact cleaner, card is not under warranty and no sticker on it for SN

Well the good news is the difference between x8 and x16 is basically nothing... https://www.gamersnexus.net/guides/2488-pci-e-3-x8-vs-x16-performance-impact-on-gpus