Overclocking a modern server processor isn't something that you hear on a daily basis. However, ServeTheHome forum user nero243 has detailed a unique method to overclock AMD's EPYC enterprise chips.
It's not possible to overclock a typical server processor in the motherboard's BIOS like you would on a desktop platform. Therefore, other methods are required, with P-state (performance state) overclocking being one of them.
A processor comes with different p-states, which allow it to function at different speeds and voltage operating points. For example, P0 is the highest state that focuses on maximum performance, while the P1 and P2 states focus more on energy-saving at the cost of lower speeds. By editing the P-states, you can essentially force the processor to run at the speeds that you want.
In a nutshell, nero243's method consists of writing the overclock settings to the processor's model-specific register (MSR). If your motherboard has a locked MSR, then you're out of luck. In order to achieve this task, the author utilized Asus' unofficial ZenStates software. ZenStates is great as it's available for both Windows and Linux users, and you can find the ZenStates-Linux code on GitHub.
As you would expect, ZenStates only works on Asus motherboards, but nero243 provides a modified version of the tool that can be executed on motherboards from other brands. If you're into tweaking, you can edit the ZenStates executable manually with tools, such as ILSpy or Reflexil. According to nero243, you just need to alter the CHECK VENDOR function, and you should be good to go. With this method, he was able to push his AMD EPYC 7551 to 3.4 GHz, with 1.3V and reach 3.8 GHz with 1.375V with 16 of the 32 cores enabled.
Before you start overclocking your AMD EPYC processor, it's important to keep your processor's Vcore (voltage core) under reasonable limits so that it doesn't trip the motherboard power delivery subsystem's overcurrent protection (OCP). It's also important to keep an eye on the power delivery subsytem's temperature, and if required, provide active cooling over it via a cooling fan. And since AMD EPYC processors are pretty heavy on the cores, you should probably cool your chip with liquid cooling to avoid thermal throttling.
There are certain limitations to overclocking an EPYC chip with the P-state process. For starters, nero243 ran into numerous problems with AGESA (AMD Generic Encapsulated Software Architecture) codes that were newer than version 22.214.171.124. He also noted that the method doesn't work with motherboards that have been updated with the BIOS revision that holds the microcode 29.