XPS 8950 + RTX 5080 FE + 1350W PSU

Hi all,

Last year I upgraded my Dell XPS 8950 with a Dell 1350W PSU. The PSU is the only one which has 4x8 pin (8=6+2). The PSU also has a MB 12 pin connector which fits well in the MB 10 pin slot. Some say the 2 extra pins that hang are 12v and GND.

Yesterday I got my Nvidia RTX 5080 Founders Edition, connected it to the XPS and I noticed POST issues.

With the RTX GPU connected, the PC does not POST if Display Port is connected to the RTX GPU. The power button error code is: “Power Rail Failure: EC ran into power sequencing failure (3 amber 5 white)”

If I manage to POST, in Windows 11 everything goes well, no issues. But when the PC enters sleep mode, it does not wake up and shows the same “Power Rail” error code or “CPU configuration or CPU failure”.

All cables fit well, never had issues.

Is this a PSU / XPS issue or a Windows 11 UEFI issues?