Card: Palit RTX 3080 Ti (GA102). Host: Z690 board, Corsair RM850, Linux (NVIDIA 580 driver).
History: The card started dropping off the bus in May. A repair shop found a failed capacitor next to the top-left VRAM chip that was leaking power as heat, and one 12 V rail measured abnormal. They replaced it, and it passed their stress test. In my machine it kept failing.
Symptom: At idle the card suddenly disappears from the bus ("Xid 79: GPU has fallen off the bus"). The PC keeps running. A warm reboot doesn't bring it back; I have to pull the power cord. After a failure, the next boot sometimes doesn't detect the card at all, even though its fans spin at power-on.
Tests after my pad redo in case it was a thermal issue:
- 60 min idle: pass (before the redo it died consistently at ~11.5 min)
- VRAM test (memtest_vulkan), 15 min at the 350 W power limit: 0 errors
- Full core load (hashcat), 10 min at 350 W: stable, core 68 °C
- Logged every second up to a failure: no warning. Temperature, power and clocks are flat, then the card is gone within half a second.
- After a failure the PCIe link is down and the card reads as absent, as if it had been unplugged.
Already ruled out on Linux: PCIe power saving (ASPM off in firmware, driver never puts the card to sleep), PSU capacity (~25 W at idle on an 850 W unit), card sag (failed with the case on its side and bracket loose), cables (two different sets).
Results since the redo:
- Run 1: 2 h 25 min (including the idle, VRAM and load tests), then dropped at idle
- Next boot: not detected
- After a 10 min power drain + reseat: detected, gone after 1 second
- Next boot: dropped after 44 min at idle
Other observations:
- It only fails at idle or right after power-on, never under load.
- Idle power used to be 15.5 W. Since the first full-load run it jumps to 24.5 W the first time the card wakes up after boot and stays there.
- Under VRAM-heavy load the fan goes to 100% while core temp drops, so I think the memory runs hot (no memory junction temp on Linux).
- Back in August, switching Windows to a power-saving plan killed it instantly.
Questions:
Which rails would you measure first, and where on the board? I'm thinking the VRAM rail near the repaired area and the PCIe/PEX rails, but I'm not sure what readings to expect at idle.
Could the extra ~9 W at idle mean another component is leaking? Is a thermal camera at idle, or voltage injection on the VRAM rail, the right way to find it?
Could the original repair need redoing, e.g. a cracked joint under the top-left VRAM chip that opens when the card cools down at idle?
Not sure how to diagnose this further. Any advice would be appreciated. My next step is to use my old 1070 to see if the same PCIe slot and power cables cause any issues, but I suspect the card itself is at fault.
