The RX 7800 XT XFX Core Edition graphics card can be used with the Gigabyte UD850GM power supply, but it's important to check a few details to ensure compatibility.

- Power: The UD850GM offers 850 watts, which is generally sufficient for most configurations including the RX 7800 XT.
- Connectors: Make sure the power supply has the necessary connectors for the graphics card. The RX 7800 XT generally requires 8-pin or 6+2 pin PCIe connectors, and the UD850GM power supply has several PCIe connectors.
- Certification: Check that the power supply is 80+ Gold certified or better, which is the case for the UD850GM model, guaranteeing adequate efficiency and stability.

In general, the UD850GM should be sufficient to power the RX 7800 XT XFX Core Edition, but a quick check of the graphics card and power supply specifications is always recommended to avoid any problems.