When PCIe x16 is set to Gen 4, system doesn't boot

System power cycles when PCIe x16 link speed in the bios is set to either Auto or Gen 4, forcing it to Gen 3 is the only way to get stability but not sure why or if this is hiding more serious issues (RTX 4070 Ti, ASRock B650M, 7800X3D).

This is a brand new build, everything was running stable until I connected the GPU. After switching the display to the HDMI port on the GPU, the system boots into Windows just fine for the first time but as soon as the Nvidia drivers are installing the system becomes unusable. The system hard resets during driver installation and continues to power cycle after that.

It sometimes does manage to boot into Windows but after 30 seconds on the desktop it will lock up and reset.

After doing some research, I've found many people with similar issues with similar systems.

What I've changed that has worked:

- Force PCIe x16 link speed in the bios to Gen 3 instead of Auto or Gen 4.
- Setting "Power management mode" to "Prefer maximum performance" in the Nvidia control panel.
- Uninstalling and reinstalling drivers in safe mode using DDU.

Since making these changes, the system is so far running stable and I'm able to run MSFS in VR and 3DMark without any issues.

What I've tried that didn't make a difference (when in PCIe Gen 4 or Auto mode):

- Re-seating the GPU and memory, multiple times.
- Re-installing Windows, multiple times.
- Using 2x PCIe cables from the PSU instead of sharing a single cable (as per instructions).
- Flashing motherboard bios (was on 1.28, now on 2.02).
- Upgrading or downgrading Nvidia drivers (tried the latest 546.33 and the older 537.xx drivers).
- Tried different cables, ports (HDMI and DisplayPort) and monitors.
- Disconnecting non-essential components, e.g. WiFi adapter, games controllers, etc.
- Monitoring all temperatures (they're all fine).
- Resetting CMOS.

Notes about my setup:

- GPU is installed in the top slot (PCIE1).
- Samsung 2TB M.2 NVMe PCIe 4.0 drive is installed in the primary M.2 slot with heatsink (M.2_1).
- GPU is connected using the supplied Y-splitter and two separate PCIe cables from the PSU.

Setup diagram: https://imgur.com/a/foW1kG9

Photo of BIOS: https://imgur.com/a/XGVAMtd

Questions:

- Should I be worried that this workaround is hiding more serious hardware/software/compatibility issues that I shouldn't ignore and might bite me later?
- Would this be a motherboard or GPU issue or something else? I'm not sure who to contact for support.
- I'm no expert with modern PCIe, could the M.2 NVMe drive be taking resource priority away from the GPU and causing it to crash? Any useful bios settings that might help?
- Is this just a software issue? Could this issue fix itself as new software/firmware/drivers are released?
- Anything else I should try?

What I find interesting is that the machine will boot stable in Gen 4 when changing it from Gen 3, but I will only get one stable session out of it, if the machine is powered off/on while still in Gen 4 mode then it won't boot again until I change it back to Gen 3. I'm not sure how relevant that is but it seems strange.

If this is normal and I just need to use Gen 3 going forward then fine, but I don't like the idea of keeping potentially faulty or incompatible hardware for the lifespan of this machine.

I already have another unboxed ASRock Pro RS board (I ordered 2 by accident) and need to return it to Amazon, but I am tempted to swap the motherboards to see if it fixes it, but if it turns out it's not a motherboard issue then I'm worried I might have issues returning it once opened.

What should I do?

Thanks,
Scott.

Hi, i have exwactly the same issues with my setup.

- B650m Pro RS Wifi (2.02 BIOS)
- AMD Ryzen 5 7600
- AMD RX6800 nonXT
- 32 GB Corsair Vengeance Mem AMD Expo)

And had the same issue with my old GTX1060 6GB GPU.

I have tried a lot of things, reseat CPU, GPU/PCIE cleaning and reseating etc..

I'm beginning to suspect i has to do with bandwidth maybe.

I can force mine to work with pcie gen4 @ x8 (8GT/s)

And you've succesfully gotten pcie x16 in Gen3 (whick is also 8GT/s)

I have created an RMA to my local supplier, but i suspect that this is more a BIOS/UEFI issue than a hardware issue. But the 2 times i've reached out to asrock i have just gotten screendump back, where they have succesfully run the same CPU/GPU combo at full gen4 pciex16 speed...