AMD maintains a site with EPYC related documentation here.
You can expect to find the following here:
Specs and Manuals
In your specific case, a solution brief exists that may answer some of your multi-chip module questions. Here is the direct link: http://developer.amd.com/wordpress/media/2017/11/LE-62006-SB-Latency-170824-Final-1.pdf
I invite you to keep coming back to the EPYC resource page linked above as we continue to add more content.