Originally Posted by Liranan
B-dies were necessary for the first and second generation Zen chips (speed and timing), but I thought this RAM compatibility had been solved in the third generation and that any kit would basically work over 2100MHz on the 3xxx's.
That is correct. Official memory support went higher mhz as well. 1st one had 2667, then 2933 and now 3200 mhz supported officially.
"With the 3rd generation Ryzen "Zen 2" processors and AMD's decision to disintegrate the memory controller from the die that has CPU cores, the memory finds itself unshackled from other low-frequency clock domains. AMD is also motivated to improve this memory controller since the doubling in CPU core-count over generations increases the demands on memory bandwidth. This dual-channel DDR4 memory controller is located in the processor's 12 nm I/O controller die (highlighted in the picture above). The two 7 nm 8-core CPU chiplets talk to this die over 100 GB/s Infinity Fabric links. At a topology-level, AMD detains the dual DCT approach to dual channel, which the company would refer to as an "unganged" interface, with two independent 64-bit paths to the memory modules instead of a blindly interleaved interface. This greatly benefits high core-count scenarios, particularly with the Ryzen 9 series chips. "
"The Infinity Fabric frequency can now either be synchronized to memory clock or unlinked from it, using various dividers. This will come in handy when running memory clocks higher than DDR4-3600, at which point the Infinity Fabric link on older generations of Ryzen processors would become unstable—on Zen 2, simply reduce the Infinity Fabric frequency and you're good to go. AMD has also introduced a plethora of new memory timing and voltage control settings that are designed to improve memory compatibility at high clock speeds."