I'm preparing to build a new PC and would like to pass my current system on to my brother-in-law, but it randomly shuts down during demanding games or benchmarks. The system has a B550M Aorus Elite motherboard, Ryzen 5 5600, 32GB of Corsair Vengeance DDR4-3200 CL16, a Gigabyte RTX 3070, and a Corsair CX650 power supply. Lowering the GPU power limit in MSI Afterburner makes the shutdowns much less frequent, although they can still happen occasionally at reduced power. I'm planning to disassemble, clean, and rebuild the PC in a different case with fresh thermal paste and new fans. What should I check first, especially to determine whether the PSU or GPU is responsible?
1 Answer
A complete instant shutdown under GPU and CPU load usually points more toward power delivery than normal overheating. Start with the PSU: check that the GPU uses separate PCIe power cables rather than one daisy-chained cable, reseat every power connector, and inspect for loose or damaged plugs. Software readings cannot fully test a PSU, so the most useful check is temporarily trying a known-good, quality unit with enough capacity. A CX650 may be borderline with an RTX 3070’s transient spikes, especially if it is older. Also test the parts separately: run a CPU-only stress test, then a GPU-only test, and then both together. If only the combined test causes shutdowns, power delivery becomes even more likely. Check Windows Event Viewer afterward, but a Kernel-Power entry generally only confirms that power was lost; it does not identify the cause.
GPU temperatures around 83–84°C are warm but normally still within the card’s expected operating range, and they should usually cause throttling rather than an immediate power cut. Check the GPU hotspot and memory temperatures too, clean the heatsink, improve case airflow, and make sure the fans are actually ramping up. If reducing the power limit reliably prevents the shutdowns, that supports either a PSU transient problem or a GPU power/thermal issue. Testing with another PSU is safer and more informative than trying to measure the PSU under load with a basic multimeter.