Stability Testing and a Good vs. Bad OC
We recommend you use Blender Benchmark or Handbrake for quick testing at different stages, they both use AVX and push the CPU cores hard. However, while they are real-world tests and reflect normal usage some users still prefer total stability, and for that, something like Prime95 needs to be used.
For the Handbrake test you can load a 4K video file into handbrake and then encode it into another format or resolution, we use the normal profile and manually take it from 4K to 1080P, it takes a few minutes and provides a mixed workload. It's not the most effective for finding long term stability, but is a good way to see if your changes are going to potentially work. The Blender benchmark is a bit easier to run, you just run it, and it's very stressful on the CPU, and it takes much longer than the HandBrake benchmark to run.
Prime95 is the go-to for hardcore stability testing. Many people run it for 24hours to determine if their stable. However, it can really hurt a CPU if your voltage is too high, and it's probably the most stress you can exert on your CPU. The blend test will test many things including RAM, but we used SmallFFTs, as those work the CPU the hardest.
We used 4.3GHz all cores with 1.43v set with LLC set to Extreme. Memory was set to 3600Mhz using XMP and no changes to timings of FCLK. Here is a bad overclock. In this case we didn't tune the SoC voltage or VDDG, so our FCLK was a bit unstable. The CPU was also quite hot, and even went over 100C. While it passed HandBrake, you can look at the Log Viewer. Our average encode speed is just 90FPS, which is how we know there is an issue with the overclock.
Here we lowered LLC to Turbo level, we also decreased voltage a little. A lot of instability can result from high temperatures, and people think they are unstable due to not enough voltage, but the truth is that high temperature is the problem. If you back off VCore you might be surprised at what happens. We also increase VCore SoC to 1.2v and set VDDG at 1.1v. You can see that the average encode speed jumped all the way to 128FPS, which is a huge increase considering we didn't change any frequency compared to the other image.
At this point, you will move on to harder benchmarks and Prime 95, in the end our CPU can only do about 4.1GHz with Prime95, although Blender benchmark will pass with these settings. It's up to you whether you will run Prime95 or other harsh stability testing programs, as they can damage the CPU, these programs we used for stability testing are designed must like other software that would be used every day. If you have any problems overclocking, you can comment on this article and we will help you out.