Intel 9900KS (5GHz boost all 8 cores).

Purchased in November 2019. Ran until December 2022 when I upgraded to a different CPU. It's been sitting on an office shelf in the box since then but I just neglected to list it.

I experimented with overclocking and found it could reach 5.2GHz all cores stable, 5.3GHz all cores marginally stable without voltage increases, but decided to just keep it at stock because I didn't need the extra speed at the time due to having an older GPU.