My PC sometimes powers off completely during gaming, with no obvious warning or blue screen. I suspect the power supply, but synthetic testing has not made the system shut down. In an OCCT extreme-load test, the RX 9070 XT reached about 400W, the CPU used around 100W, the GPU core temperature was 53°C, the hotspot reached 110°C, and the CPU reached 75°C. While gaming, AMD Adrenalin also showed the GPU staying below roughly 400W. Could transient power spikes be overwhelming the PSU, or could the shutdown be caused by a wiring, temperature, driver, or game-specific issue? My system uses a Ryzen 7 7800X3D, RX 9070 XT 16GB, 32GB of RAM, Corsair RM750e 750W PSU, ASUS Prime LC 360 ARGB cooler, and MSI MAG PANO 110R PZ case.
3 Answers
Find out whether this happens in every demanding game or only one title. If it is game-specific, update or clean-install the graphics driver, remove any overclocking software, and check for game or driver crashes. If the entire computer instantly loses power across multiple games, that points much more strongly toward PSU protection, cabling, overheating, or a motherboard power issue than toward a normal application crash.
The 110°C GPU hotspot is worth checking too. It may be within the card's limit, but the gap between the core temperature and hotspot is fairly large. Check that the cooler is mounted properly, the fans are working, the case has good airflow, and the card is not sagging or making poor contact. Also check Windows Event Viewer for Kernel-Power errors, though that usually only confirms that power was lost rather than identifying the cause.
The PSU is the first thing I would investigate. A GPU showing 400W in monitoring software can still produce much higher, very short transient spikes. A 750W unit may run the system normally but lack enough headroom when the GPU and CPU spike at the same time. Make sure every GPU power connector is fully seated and use separate PCIe cables rather than one daisy-chained cable. A quality 850W or higher unit would give you more margin, although that does not prove the current PSU is defective.
I have not changed the card settings, and undervolting it after the shutdowns started did not completely solve the problem. I am worried about whether these sudden power-offs can damage the other components.

It happens when playing demanding games that use the GPU heavily, rather than during ordinary desktop use.