I think you missed the biggest reason this doesn't do much for servers - they already run at low frequencies & voltages. For example take the Epyc 7742, at 225

I think you missed the biggest reason this doesn't do much for servers - they already run at low frequencies & voltages. For example take the Epyc 7742, at 225W it sounds super power hungry. But the 64-core chip only boosts to 3.4ghz max (2.25ghz base). That's less than the base clock of almost any of the Ryzen consumer CPUs. And if you look at the lower frequency end of https://images.anandtech.com/doci/16214/PerCore-1-5950X.png https://images.anandtech.com/doci/16214/PerCore-1-5950X.png there's not a whole heck of a lot of efficiency gains likely to be had below that ~3-3.4ghz mark. They're already basically sipping power at something like 3w per CPU core or less. 225w / 64c = 3.5w/c, but the IO uncore isn't exactly cheap to run and iirc sits more like in the 50-70w range. So subtract that out and you're at more like 2.5-2.7w/c. I don't think throwing cooling at this is really going to get you much of a gain.