The high temperature reading (100°C) on "temp #4" and the negative temperature reading you mentioned are concerning. These could indicate a sensor malfunction or a short circuit on the motherboard. If the temperature sensor is faulty or shorted, it could send incorrect data to the system, potentially causing the motherboard to shut down as a safety precaution.
Solution:
Check the BIOS settings to see if any temperature limits have been set too low, which might be triggering the shutdown.
If the motherboard is newly upgraded, it’s possible that the socket or power delivery could have issues, especially if the motherboard was not designed for such high-end parts. Double-check your motherboard’s compatibility with the Ryzen 9 5950x and make sure the power delivery components are in good condition.
If you’re seeing strange sensor readings, try using software like HWMonitor or Core Temp to monitor the temps and see if they match up with the BIOS or motherboard readings.
2. Power Supply (PSU) Issue
Even though you've replaced the PSU, there could still be an issue, especially with the increased power demands of the new Ryzen 9 5950x and RX 7800XT. An 850W PSU should generally be more than enough for your system, but PSU failure is still possible if it was a lower-quality model or if there was some issue during installation.
Solution:
Double-check that all power cables are properly connected, particularly the 24-pin motherboard connector and the 8-pin CPU power connector. Sometimes these cables can become loose or improperly seated, causing instability.
You could try using a different, known-working PSU to see if the issue persists.
3. CPU Stress Test and Overheating
You mentioned that your system shuts down after about 4 seconds of a CPU stress test. This suggests a thermal issue or power delivery problem. Even though your temperatures are within the typical range under load (59-75°C for CPU), it's still possible that there is an issue with your CPU cooler installation, thermal paste application, or the NHD15 cooler's contact with the CPU.
Solution:
Make sure the NHD15 cooler is properly installed and making good contact with the CPU. If you haven't reapplied thermal paste after installing the cooler, you should consider reapplying thermal paste and ensuring a proper fit.
Consider checking the BIOS settings for any overclocking or power settings that might be too aggressive, causing the CPU to shut down under load.
Ensure your cooler fan speeds are functioning properly and that airflow is good inside the case.
4. Driver and Software Issues
It's possible that the drivers (especially GPU or chipset drivers) are not fully compatible with your new hardware. Even though you cleaned the old GPU drivers, there could be remnants or conflicts causing instability.
Solution:
Use Display Driver Uninstaller (DDU) to clean out any remnants of the old GPU drivers completely, and then install the latest drivers from the AMD website for both the CPU and GPU.
Ensure that Windows is fully up-to-date, and consider reinstalling it if the issue persists, as sometimes old OS configurations may not play well with new hardware.
5. Memory or Motherboard Failure
If there is a fault with the motherboard or memory (RAM), it could cause power loss under load. Sometimes faulty RAM slots or improperly seated RAM can cause these kinds of issues.
Solution:
Try re-seating the RAM in its slots, ensuring that they are properly installed and that there are no visible issues with the RAM or the slots.
Run memtest86 or use Windows Memory Diagnostics to check the integrity of the memory.
6. Other Miscellaneous Causes
Windows Power Settings: Ensure that your power settings are configured correctly in Windows. Set your power plan to High Performance to avoid any unnecessary throttling that could cause shutdowns.
BIOS Settings: Resetting the BIOS to default settings can sometimes resolve issues, particularly if there were any incorrect configurations after the upgrade.
Conclusion:
Given that your system worked fine before the upgrade, the most likely causes of the issue seem to be either motherboard sensor malfunctions, power delivery problems, or a cooling issue. Since you replaced the PSU and cooler, I’d suggest focusing on the motherboard and thermal issues first, particularly looking into those strange temperature readings, and ensuring the CPU cooler is properly seated.
For more in-depth help with Ryzen 9 issues, you might want to check out Tom's Hardware, where they have extensive resources on troubleshooting high-end AMD CPUs.
