The AMD Threadripper 1950X has been successfully overclocked to 5.2 GHz on all 16-cores using LN2. This represents a 40.5 percent increase over the base turbo clock speed and gives a Cinebench R15 multi-core score of 4122.
https://www.notebookcheck.net/Threadripper-1950X-benchmarked-at-5-2-GHz-on-all-cores-using-liquid-nitrogen.241680.0.html