PC randomly loses power and restarts despite a 1200W PSU and UPS
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MellowPine47
My three-year-old PC has suddenly gone black and restarted twice within two weeks. The first failure happened while playing a demanding modded Minecraft server, but the second occurred while I was only browsing YouTube. Event Viewer only reports an unexpected shutdown after each incident, with no warning immediately beforehand. The system has an Intel i9-13900K, RTX 4090 OC, 64 GB of DDR5-6400 memory, a Gigabyte Z790 motherboard, and a Thermaltake GF3 1200W 80 Plus Gold power supply. It is also connected to a CyberPower 1000W UPS. The CPU has a mild undervolt, and I'm trying to determine whether this is a hardware, stability, or power-related problem.
Answers
An unexpected-shutdown event usually only records the aftermath, so it won’t identify what caused the power loss. Since the CPU is undervolted and the memory is running at a high XMP speed, start troubleshooting by returning the BIOS to defaults. Disable the CPU undervolt and XMP, then test for a while. If the restarts stop, add those settings back one at a time or use a less aggressive memory speed. Also check the UPS load and whether it is rated for the system’s brief power spikes; a 1000W UPS can be marginal with a 4090 and 13900K even when the PSU itself is 1200W.
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MellowPine47: The only Event Viewer entries around both incidents appear after the restart, with nothing recorded immediately before the power cut. I’ll test with the undervolt and XMP disabled and check whether the UPS is being overloaded.