Earlier quoted context omitted.
Yeah, it's real obnoxious of Intel to silo ECC support off into the Xeon line, isn't it? I switched to ECC memory in 2013 or 2014 with a Xeon E3 (fundamentally a Core i7 without the ECC support fused off) and of course a Xeon-supporting motherboard (with weird "server board" quirks: e.g., no on-board sound device). I love that AMD doesn't intentionally break ECC on its consumer desktop platforms and upgraded to the T…
I've considered using an AMD CPU instead of Intel's Xeon on the primary desktop computer, but even low-end Ryzen Threadripper CPUs have TDP of 180W, which is a bit higher than I'd like. And though ECC is not disabled in Ryzen CPUs, AFAIK it's not tested in (or advertised for) those, so one won't be able to return/replace a CPU if it doesn't work with ECC memory, AIUI, making it risky. Though I don't know how common i…
Any apples-to-apples comparable Intel CPU will have comparable power use. The difficulty is that Intel didn't really have anything like Threadripper — their i9 series was the most comparable (high clocks and moderate core counts), but i9 explicitly did not support ECC memory, nullifying the comparison.
You're looking at 2950X, probably? That's a Zen+ (previous gen) model. 16 core / 32 thread, 3.5 GHz base clock, launched August 2018.
Comparable Intel Xeon timeline is Coffee Lake at the latest, Kaby lake before that. As far as I can tell, no Kaby Lake nor Coffee Lake Xeons even have 16 cores.
The closest Skylake I've found is an (OEM) Xeon Gold 6149: 16/32 core/thread, 3.1 GHz base clock, 205W nominal TDP (and it's a special OEM part, not available for you). The closest buyable part is probably Xeon Gold 6154 with 18/36 core/threads, 3GHz clock, and 200W nominal TDP.
Looking at i9 from around that time, you had Skylake-X and a single Coffe Lake-S (i9-9900K). 9900K only has 8 cores. The Skylake i9-9960X part has 16/32 cores/threads, base clock of 3.1GHz, and a nominal TDP of 165W. That's somewhat comparable to the AMD 2950X, ignoring ECC support.
Another note that might interest you: you could run the Threadripper part at substantially lower power by sacrificing a small amount of performance, if thermals are the most important factor and you are unwilling to trust Ryzen ECC: http://apollo.backplane.com/DFlyMisc/threadripper.txt
Or just buy an Epyc, if you want a low-TDP ECC-definitely-supported part: EPYC 7302P has 16/32 cores, 3GHz base clock, and 155W nominal TDP. EPYC 7282 has 16/32 cores, 2.8 GHz base, and 120W nominal TDP. These are all zen2 (vs 2950X's zen+) and will outperform zen+ on a clock-for-clock basis.
> And though ECC is not disabled in Ryzen CPUs, AFAIK it's not tested in (or advertised for) those, so one won't be able to return/replace a CPU if it doesn't work with ECC memory, AIUI, making it risky.
If your vendor won't accept defective CPU returns, buy somewhere else.
> Though I don't know how common it is for ECC to not be handled properly in an otherwise functioning CPU; are there any statistics or estimates around?
ECC support requires motherboard support; that's the main thing to be aware of shopping for Ryzen ECC setups. If the board doesn't have the traces, there's nothing the CPU can do.