CPU

Overclocking

TODO I have not yet looked for system-tools for overclocking

Testing

More Testing Tools can be found on the ArchWiki

Prime95/Mprime

$ mprime
Select "No" when asked to join the distributed computing project
16 for torture testing
Recommended test: 2

This application includes hardware error checking. Output to the CLI as well as the logfile.
Check the file results.txt

ffmpeg video encoding

This command encodes random noise with x265 and discards the resulting video
$ ffmpeg -y -f rawvideo -video_size 1920x1080 -pixel_format yuv420p -framerate 60 -i /dev/urandom -c:v libx265 -preset placebo -f matroska /dev/null

ArchWiki Source

Stress

Stress is capable of testing CPU, memory, I/O and disks
Use $ stress -c (threads) to test the CPU