My sister has an older PC with an Intel i5-9400F, MAG B365M Mortar motherboard, and 16 GB of RAM. Her previous graphics card started showing artifacts, so she recently installed an RTX 5060. The computer works normally for a while, but sometimes the screen suddenly goes black and the system restarts without warning. Driver cleanup and reinstallation with DDU did not fix it. The power supply is a Seasonic S12II-620 Bronze. Could the PSU be causing the crashes, or is another component more likely? She does not game very often and would prefer a practical fix that lets her use the PC normally before upgrading the rest of the system.
2 Answers
A 620W unit should be enough on paper for an RTX 5060, so the wattage itself is probably not the issue. However, the S12II is an older design, and its age and condition matter more than the label. Sudden black screens followed by an immediate restart can happen when the PSU protection trips, especially if the unit is several years old. Check that the card is fully seated, use the correct dedicated PCIe power cable if required, and inspect the connectors. If the PSU is old, replacing it with a modern, reputable unit would be a sensible first hardware upgrade.
Do not assume the old CPU or motherboard is automatically causing the restart; they may bottleneck the card in some games, but bottlenecking normally causes lower performance rather than an instant reboot. Check Windows Event Viewer for Kernel-Power errors, monitor CPU and GPU temperatures, and test the system with a stress test. Also try reseating the GPU and RAM. If temperatures are normal and the crashes continue, the aging PSU is the strongest suspect, even though its 620W rating is technically sufficient.
If replacing the PSU, choose a current model from a reputable brand with the appropriate native GPU connector rather than relying on questionable adapters. A quality 550–650W unit should be plenty for this system.
The graphics driver has already been completely removed and reinstalled with DDU, so a basic driver corruption problem seems less likely. I would test with another known-good PSU if possible before buying other parts.