OCCT

Pros

• Highly effective at identifying specific hardware failures, such as faulty power supplies or VRAM errors.
• Provides granular feedback, such as identifying which specific core or thread is producing errors.
• Versatile toolset that includes standalone tests for memory, CPU, power, and GPU stability.
• Reliably reproduces system crashes to help diagnose intermittent hardware issues.

Cons

• Can cause total system unresponsiveness or freezes if process priorities are set to 'Realtime' during testing.
• Temperature readings may occasionally conflict with other monitoring software like NZXT CAM.
• Memory testing is limited by the inability to scan addresses currently occupied by the operating system.

Caveats

• Some users consider the extreme loads 'unrealistic' compared to real-world usage scenarios.
• While excellent for stability, it is often used in conjunction with other tools like Memtest86 or Prime95 for comprehensive verification.
• A demo version is available, but some advanced features may require a license.

Best for

• Stress testing new PC builds for stability.
• Verifying overclocks or undervolts on CPUs and GPUs.
• Diagnosing suspected power supply (PSU) failures.

Avoid if

• You only need a performance benchmark rather than a stability stress test.
• You are uncomfortable pushing your hardware to its absolute thermal and power limits.