There are 2U dual EPYC servers e.g. from Supermicro

https://www.servethehome.com/dual-amd-epyc-7601-processor-pe...

The Dell EMC PowerEdge R7425 is a dual Epyc server in 2U format, sold by Dell. The top end Epyc chip gets you 64 cores (128 threads). The core density is competitive, along with its supported IO device (eg: NVMe drive) density.

Supermicro blows AMD out of the water when it comes to density.

Here's equivalent 4 node in 2U AMD systems (they differ based on disk configuration -- SAS, NVME, or a mix of both). They also support Supermicro SIOM, so you can choose what integrated networking you want:

http://www.supermicro.com/Aplus/system/2U/2123/AS-2123BT-HNC...

http://www.supermicro.com/Aplus/system/2U/2123/AS-2123BT-HNR...

http://www.supermicro.com/Aplus/system/2U/2123/AS-2123BT-HTR...

If you wanted even more density, there's the MicroCloud and MicroBlade series (although they use Intel processors):

https://www.supermicro.com/products/MicroBlade/

https://www.supermicro.com/products/nfo/MicroCloud.cfm

That being said, these don't make a lot of sense unless you're very space-constrained, or your racks have a ton of power available. Given a 30A 208V circuit, I could only safely run three of the above AMD systems at full power. I'd rather just get dedicated 1U or 2U servers, and not have to make compromises about expandability or serviceability.

thanks for the links. I hadn’t found any vendors on those 4 node systems.