Changing PCIe gen4 to gen3 blind

[Obby]

My friend reset his BIOS settings to default. His PC is a prebuild with hardline water-cooling. GPU is not directly on motherboard but rather on a riser - which is a Gen3 PCIe. We now have no display output and with no integrated graphics we cannot see BIOS to change the settings back.

We are asking for help with navigating to the settings while being blind. Thank you for your help.

[Jiaszzz_ROG]

Hello @Obby 

Due to the ongoing local holidays in our area, our response time may experience delays.
We apologize for any inconvenience the delayed replies may have caused.
Could you please confirm, when there is no video signal output, is the PC build able to power on successfully, does the CPU fan function, or is there no power at all? Are there any Q-LED indicator lights on, such as the white VGA light?
Based on your description, we recommend installing the GPU directly into the ROG Strix TRX40-E Gaming PCIEX16_1 slot, rather than using an extension cable, to check the display issue and rule out potential hardware problems.

Please refer to the FAQs below, and if necessary, please cross-test with different PCIe slots or another GPU.
[Motherboard] Troubleshooting - No Power/No Boot/No Display
[Motherboard] ASUS motherboard troubleshooting via Q-LED indicators

Thank you.