When using Prime95 for stress testing, users often encounter common issues that can impact the accuracy and reliability of the tests. Below is a detailed guide on troubleshooting these issues, along with potential solutions:
1. Fatal Error: Rounding
One of the most frequent errors encountered during Prime95 stress tests is the “Fatal Error: Rounding.” This error typically indicates instability in the CPU, often due to insufficient voltage, high temperatures, or issues with memory. To address this:
- Increase CPU Voltage: Insufficient voltage is a common cause of this error. Incrementally increasing the CPU Vcore in your BIOS by small amounts (e.g., 0.03 to 0.05V) can stabilize the system. However, be cautious as this will also increase CPU temperatures, so ensure your cooling solution is adequate.
- Clear CMOS Battery: Sometimes, outdated or conflicting data stored in the CMOS battery can cause instability. Clearing the CMOS battery may resolve these conflicts.
- Address High Temperatures: If your CPU runs hot, ensure that your cooling system is efficient. Overheating can cause errors during stress tests, so consider upgrading your cooler or improving airflow within your case.
2. Worker Failures
Prime95 runs multiple “workers,” each corresponding to a CPU core or thread. Sometimes, users report that one or more workers fail while others continue without issue. This usually points to problems with CPU stability, memory, or even the power supply:
- Test Memory Stability: Run memory diagnostics such as Memtest86+ to check for errors. Sometimes, increasing the DRAM voltage slightly (e.g., by 0.005V) can resolve instability related to memory.
- Check Power Supply: An underpowered or failing power supply unit (PSU) can cause worker failures. Ensure your PSU can deliver adequate power, especially when running a high-performance CPU under load.
- Use Older Prime95 Versions: Some users find that newer versions of Prime95, especially those using AVX/AVX2 instructions, cause excessive stress leading to failures even on stable systems. Reverting to older versions like Prime95 26.6, which does not use AVX, can sometimes yield more reliable results.
3. System Crashes and Reboots
System crashes or reboots during Prime95 testing are often related to hardware issues such as overheating, PSU overload, or CPU instability:
- Reseat Components: Ensure that all components, including RAM, CPU, and power connectors, are securely seated. Loose connections can lead to instability under load.
- Monitor Temperatures: Use software tools like HWMonitor to track your CPU temperatures during stress tests. If temperatures are excessively high, consider improving cooling or reducing the clock speed of the CPU.
- Evaluate Power Supply: A PSU that cannot handle the power demands of your system under full load can cause reboots. Upgrading to a more robust PSU might be necessary if crashes persist during stress testing.
4. Prime95 Hangs or Fails to Start
If Prime95 hangs or fails to start, it may be due to incorrect settings or hardware incompatibilities:
- Check FFT Size Settings: Prime95 uses Fast Fourier Transforms (FFTs) of specific sizes during testing. Ensure the FFT sizes you’ve set are supported by Prime95. Using unsupported sizes can cause the program to hang.
- Run Without AVX: If Prime95 fails to start or crashes immediately, try disabling AVX in the settings. This can help avoid overwhelming the CPU, especially if it has a known vulnerability to high AVX workloads.
5. Inconsistent Test Results
Sometimes, users observe that Prime95 tests produce inconsistent results, such as passing one day but failing the next:
- Environmental Factors: Variations in ambient temperature can impact CPU performance. Ensure your testing environment is consistent, and avoid running tests in overly warm or cool conditions.
- BIOS Settings: Inconsistent results may stem from BIOS settings being altered by automatic updates or tweaks. Double-check your BIOS settings, particularly those related to power and voltage, before starting a new test.