I started a new build with a liquid cooler connection not fully plugged in. The CPU reached 93 C while I was in BIOS for about five minutes, then I shut it down.
I reconnected the cooler and reapplied thermal paste. The PC now runs and I installed Windows, but someone told me the CPU must be permanently damaged. Is that likely, and how can I check?
Permanent damage sounds unlikely from what you described. Modern CPUs monitor their temperature and can reduce performance or shut down to protect themselves. Those safeguards aren't an absolute guarantee, but a brief overheating episode followed by normal operation is reassuring.
Don't throw the CPU away based on that. Keep an eye on CPU temperatures and stability now that the cooler is connected.
For the Ryzen 7 9800X3D, the specified maximum operating temperature is 95 C, so the 93 C reading was high but below that limit. The temperature shown for the liquid cooler afterward isn't necessarily the CPU temperature, though. Check the CPU sensor in monitoring software as well.
Also, reaching a temperature limit doesn't necessarily mean an immediate shutdown. The processor may throttle first, depending on conditions.
Installing Windows is a good sign, but it doesn't prove the CPU is stable under heavy load. Once you've confirmed the pump and radiator fans are running, try a CPU stress test while watching the CPU temperature and clock speeds.
Cinebench is one option for a short test. Stop the test if temperatures climb rapidly, the cooler isn't working, or the system becomes unstable. A clean run is reassuring, although no single test can prove there's no damage.
Double-check the cooler's installation guide for the pump, fan, power and screen connections. A working screen doesn't by itself confirm that the pump is running. Make sure the radiator fans spin too, then check the CPU temperature in BIOS or monitoring software.
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v81!parcel_2:
Some temperature increase under a heavy test is normal. Watch for sustained throttling, crashes, or temperatures that suggest the cooler still isn't doing its job.