XPS 8920, Radeon 6650XT, stuck before BIOS !

Hi everyone,

I've been a regular reader of this forum for a few years. I learnt a lot from you all to cool my XPS 8920 case

Now, it's my turn to post about an issue though...

CONTEXT:

• I decided to upgrade my aging GeForce 1070 GPU. 
• After a lot of reading: I decided to go for an ASUS Dual OC Radeon RX 6650XT
• Key specs of this GPU:
  • PCIe Gen4 (but can be used via PCIe Gen3 on older motherboards)
  • PCIe x16 slot required, however the GPU operates in PCIe x8 (only the first 8 connectors get power)
  • 8-pin power connector required
  • Fits the XPS 8920 case very well (length, width)

THE ISSUE NOW...

• When I boot my PC, I get stuck at the DELL boot screen
• I can somehow use the keyboard arrows to push the boot sequence forward to the point where I am offered to press F2 to access the BIOS
• The thing is: I can't access the BIOS. I remain stuck at the DELL screen.
• However: when I switch on the computer, I can see the card gets proper power, since the fans start spinning for a few seconds, until I get stuck on the DELL boot screen (then fans turn themselves off. It could be the "fan off" 0Db feature of the GPU, when its temp is low)

MY PC SPECS:

• Dell XPS 8920 motherboard
• Core i7-7700 (non K)
• 2x8GB of RAM at 2,400 Mhz (according to the BIOS itself)
• Seasonic 750W PSU (Gold standard)
• I use a 6+2pin connector to connect the PSU to the GPU (just like on my old GeForce 1070)

BOTTOM LINE:

Does anybody have any theory as for why I've got this issue? Any possible fix?

The PSU is powerful, so I doubt it's a power problem.

Could the motherboard be the issue i.e. it's not able to host the GPU via PCI Gen3 (while it should); or not able to accept its PCIe x8 format (within the PCIe x16 slot)?

Frustrating. HELP!  

Thanks!