Prime95 Troubleshooting
When Prime95 stops, crashes or reports an error, the starting point comes from the program’s own stress.txt guide: suspect the hardware first. The Torture Test compares every result against a known correct answer, so a mismatch usually means the machine calculated wrong under load. A software bug is only the likely explanation when the exact same error repeats at the exact same place every time; in that case the developers ask users to report it on the Mersenne Forum.
First triage: read the failure before changing anything
Note which worker stopped, which FFT size was running, and how long the test ran before failing. A failure in Small FFTs points toward the CPU cores, cache or cooling. A failure in Large FFTs or Blend, while Small FFTs passes, points toward memory or the memory controller; the Torture Test menu itself gives that hint. Return the system to stock settings before retesting, so you change one variable at a time.
FATAL ERROR: Rounding
Why the rounding error appears, why it points at hardware instability, and how to isolate the failing core or memory setting.
Hardware Failure Detected
What this message means, the order in which to check overclock, memory and cooling, and when to suspect the software instead.
Prime95 Reaches 100°C
Why Small FFTs is the maximum heat preset by design, what to check in your cooling, and when to stop the test.
Crashes and Blue Screens During Prime95
How to work through a crash or BSOD under load, from stock settings to memory and power checks.
A Worker Has Stopped
One worker stopping usually identifies the unstable core or thread. Here is how to find it and what to adjust.
AVX Offset Explained
How an AVX offset lowers clock speed under AVX loads on Intel platforms, and how it interacts with Prime95 testing.
Prime95 Errors vs an Unstable System
The line between a test that found real instability and a run that was configured or interpreted incorrectly.
Using Prime95 as a Memory Test
Large FFTs stress the memory controller and RAM, but dedicated tools test memory differently. Know the limits of each.
Is Prime95 Safe to Run?
There is no official safe duration promise. What the documentation actually says about heat, monitoring and personal risk.
Related hubs
For correct setup before you retest, see the tutorials hub. For the current verified release, visit the download page.