I'm considering doing 1920x's in either 1U or 2U. For a mild to moderate load VMWARE lab in my office. Based on my desktop experience with TR, that processor can hot-spot burst up temps and practically boil water out of a liquid cooling system like nothing I've ever seen before. I think 2U is definitely the platform to fit it into, simply because the CPU is going to need all the help it can get. 1U is better left for the Epyc 3000 and lower power SP4 Epyc CPUs. Dynatron makes excellent coolers, and I'm considering that exact model. With the better functioning PBO in TR gen 2, I'd keep a close eye on thermal management, I don't know how well ASROCK's firmware is set up yet for that TR server board. I also hope that you don't intend to fill the drive bays up with spinning SAS drives as it will add a lot of thermal load to the case.
With a 2950X its going to get hot, especially in a use case where you're going to be loading down all cores. You might be better off going with 3-4 U and looking at a WraithRipper cooler or even a Coolermaster ML360-TR4 (what I use for my present 2920X) which from what I've seen in testing can even load up those high capacity solutions. In the end, a more thermal optimized solution like EPYC that can run at top clock speeds in a smaller form factor might be far better than a TR that's constantly thermally throttling itself. These are my musings, apologies if it seems a little rambling. I hope it encourages more discussion on this topic.
I appreciate the insights, and it's a relief to hear I'm not the only one considering this type of build.
I looked at some 1U chassis, but I have doubts about the passive heatsinks, and that 1U active Dynatron looks like it would commit suicide in my render builds.
The 2U looks right to me with adequate airflow, and the A26 does look capable. I could use PB2 to limit the wattage to try to prevent thermal throttling and ease the stress on the chips. Stability is more important for me that maximum boost clocks, but a little bit of OC would be nice.
No SAS drives - only flash for speed and reliability.
I looked at 4U config with the Noctua U9 cooler, but that would take up a lot of rackspace which gets expensive. I also considered 2990WX builds in those 4U chassis, but again the space constraints are a real issue. I may shift back towards 4U if the next-gen Threadripper are compelling enough - if I could do 64 core at 250w it would be worthwhile I think.
I am also very interested in Epyc, and I look forward to tomorrow's announcement and review. However the cost difference is considerable, and my use case doesn't benefit much from the extra PCIe lanes and memory channels - at least not enough to be worth it. Again, depending on Rome I may go for them (or discounted Naples), but this 2U 2950X config makes sense right now.
The nice thing about this config is it offers good performance for both core-optimized and frequency-optimized rendering - a good all-around render setup.
This entire config may become moot in 10 hours, but it is something I've been thinking about for awhile and wanted to share and get feedback.