Just as information for some later readers, but this is applicable not just to Epyc but also the consumer version Threadripper. My understanding is that this is an example of a Non-Uniform Memory Access (NUMA) which was also used to link multiple cpus in different sockets together for a long time now, but now they've been integrated into a cpu that fits in one socket.

This actually has an importance if you are running a VM on such a system since you'll run into things like the actual RAM (not l3 cache) is often directly linked to a particular NUMA node. For example accessing memory in the first ram stick vs the second will give different latencies as it goes from ccx1 => ccx2 => stick2 versus ccx1 => stick1. This is applicable to I think 2XXX versions and earlier for threadripper. My understanding is that they solved this in later versions using the infinity fabric (IO die) so now all ccx's go through the IO die.

I ran into all of this trying to run an ubuntu machine that ran windows using KVM while passing through my nvidia graphics card.