Comment by exabrial

Up to a certain point and It’s actually very dependent on the CPU.

Take Epyc processors. On certain ones, after certain RAM amount, populating all the slots causes the cpu to kick the RAM speed to a lower tier.

You’re then limited to capacities of two sticks.

Weird, but it has to do with power requirements. Abutting above the threshold had to be buffered, which increases latency.