Z370 ROG MAXIMUS FORMULA X - PCIE BANDWIDTH SHARING with M.2 slots and cpu

[jin1995]

SPECS : 

i7 8700k ocd to 4.8ghz
rtx3080ti msi suprim x ( pcie 3.0 x16)  slot 

32gb trident g skill ram(2 *16gb  slot next to cpu)

maximus formula x motherboard

corsair aio h115i

samsung 960pro m.2_1 slot

 samsung 990 pro M.2_2  slot 

evga 750w gold psu

The pcie slot of my card  drops randomly from 8 to 4 to 1.1 x3 .  in gpu z and i am seeing a drop in games.  and it doesnt  increase above 4 ever . lately.  but i do remember seeing it at 16 and 8 earlier with better performance . 

 x8 slot is not working well. so  i can only use the x16 slot .


 i want to know if using both the m.2 _1 and   m.2_2 slots on this  drops the performance of the gpu pcie lanes further ? there is not enough clarity in manual it just says sata ports 5/6  get disabled but i am not using any sata ports .

I have tried reseating the gpu as well without much luck .

Kindly let me know whats causing it i currently game 1440p and prefer above 100fps so the current setup is not an issue for me and i would preferrably upgrade the full system  only when rtx 5090 is out  .

[jin1995]

 please note ,  since some time i donot see the x16 slot read above x4 in gpu z ever .  i want to be sure if it is a faulty lane  or some lane sharing between the m2 drives causing the issues

[Jiaszzz_ROG]

Hello, @jin1995 

May I inquire if the situation you described occurred following any recent changes, such as a BIOS update or the connection of an external device?
Could you confirm if the current BIOS version is 2701 and whether there is any use of adapter or extension devices for the GPU?
Upon investigation, it appears that your GPU interface is PCI Express® Gen 4, while the expansion slot specification for the ROG MAXIMUS X FORMULA is PCIe 3.0. This may lead to specification differences, potentially limiting optimal performance.
Additionally, according to the user manual, PCIe and M.2 slots do not share bandwidth.
We recommend checking for any overheating issues and inspecting the GPU's gold fingers or slots for dust or damage.

Thank you.

[jin1995]

Yes the Bios Version is 2701.
No this didnot occur due to any recent changes. Only recent change i've made is adding the ssd in m.2_2 slot.

Gpu being gen 4 is fine.

My trouble is i should be getting gen 3 x 16 speeds  in the topmost slot but i am getting only gen 3 x4 .

Th gpu doesnt seem damaged.

Please note in the motherboard when i check dmi info in the bios it reads only 4 lanes there as well for the gpu.
i am really puzzled as to whats the issue?

Would love if anybody can help mesolve this .

[Jiaszzz_ROG]

Hello, @jin1995 

May I kindly ask for the following information to better verify your situation?
- the images of the setting in BIOS, or whether it is the default
- is the issue still persisting after clearing CMOS?
- are there any extensions or adapters used to connect any devices, such as GPU or SSD?
- the OS version and OS build
- screenshots of the GPU-Z or any other relevant software showing the operational channels for the GPU
If possible, we recommend cross-testing with another GPU to isolate any potential hardware issues.

Thank you.