The Ryzen 9 3900X is limited to DDR4-2933 when using four modules, whereas AMD’s official spec says the CPU will handle DDR4-3200 with just two modules.
Depending on how good the silicon is, the integrated memory controller might do better than that. Our chip handles right up to DDR4-3600 CL16 memory with four modules, but whatever the limit, the point is, it will go higher with just two modules.
Dual-ranked modules introduce a new set of limits, though none were explored in this article. AMD lists the official dual-ranked DIMM support as DDR4-3200 for two modules, but just DDR4-2666 when using four modules.
It would be interesting to see how two and four dual-ranked modules compare in these dual-channel systems, but that’s a test for another day.
https://www.techspot.com/article/1971-more-ram-modules-better-for-gaming/