Why does my GPU keep failing with Xid 79 fallen off the bus?
“Xid 79 GPU has fallen off the bus” is one of those errors that is really difficult to diagnose remotely, as it can have many root causes, including defective hardware. PSU should be dimensioned such that the total combined wattage of all power system components does not exceed 60% of the PSU’s power rating. I would suggest PSU rated 80 PLUS Platinum, they are more efficient and typically use higher-quality components. Make sure all PCIe power connectors are properly connected (fully inserted, locking tab engaged). Do not use Y-splitters or 6-pin to 8-pin converters in any of the PCIe power cables supplying the GPU. Make sure GPU are inserted properly into their PCIe slots and are mechanically secured via their bracket to avoid mechanical strain on the PCIe connector.

Here are some potential reasons why this error may appear:

- Power issues: If the GPU is not receiving enough power, it may disconnect from the motherboard and cause this error.

- Overheating: If the GPU is overheating, it may shut down to prevent damage and cause the Xid 79 error.

- Driver Issues: Outdated or incorrect GPU drivers can also cause this error.

- Hardware Failure: The GPU itself could be malfunctioning and causing this error.

You also could try a BIOS update or plug it into a different slot to test if only one slot is affected. If the problem persists, it may be best to contact the manufacturer for further support or to consider replacing the GPU.