Daonayt

It does have only one connector and it's just not possible for this system to draw anywhere near 500W. Guess I will have to send the system to service. It's awkward cause I have to send it to a different city. So much for Gigabyte Ultra Durable, I guess.

Is there any other UEFI option I can try or is the motherboard faulty?

I get an occasional shutdown during gaming and other load scenarios. Everything turns off except the PSU, with the PSU fan very loud. Usually during gaming the PSU is pretty cool and almost inaudible. I can't turn the PC back on, unless I flip the switch on the PSU. I thought I fixed this by selecting the Power loading option in UEFI (description: Enables or Disables Dummy Load. When the power supply is low load a self protection will activate causing it to shutdown or fail. If this occurs please set to enabled.) But a few days ago, after months of no problems during summer and warm tepmeratures, it happened again. I checked, and the Power loading is enabled. I am using an RX580 and a Ryzen 5 2600, no overclocking. CX450 should be powerful enough for this.