> How do you do that? Is it a setting in the bios? Or can it be done runtime?
On AMD, it's a utility you run. I believe you may require a reboot to apply it. On some Intel platforms, it's been settings in the BIOS.
> It sounds interesting if I can run a beefy rig as a power efficient device, for always-on scenarios, and then boost it when I need.
This is what the processor is doing internally anyways. It throttles voltage and frequency and gates cores based on demanded usage. Changing the TDP doesn't change the performance under a light-to-moderate workload scenario at all.
Ryzen Master lets you change some of the tuning for the choices it makes about when and how aggressively to boost, though, too.