Some problems arise when using 4 DIMMs with 3rd Gen Ryzen processors.
Some problems arise when using 4 DIMMs with 3rd Gen Ryzen processors.
Using multiple DIMMs on the same channel adds extra strain on the cables. Weak memory controller performance together with increased resistance in the motherboard traces may cause it to underperform. Generally, a solid memory controller can handle most configurations, but because this setup is close to the limit, the layout becomes more noticeable.
You're looking for a specific B450 board, probably one with a topology for 4x32. It seems the main concern is the IMC, as quad rank puts a lot of stress on it and Zen 2 still has decent performance but the IMC feels okay. For RAM, you should opt for high-quality 32GB sticks—micron 16Gb is light on the IMC and should give you decent speeds. If you anticipate needing more RAM later, go with AMD EPYC chips. Current prices are around $200 for CPUs like the 7302 and 7551, with the 7281 at about $90. DDR4 memory is very affordable and offers many cores at low cost, though Zen 2 and newer EPYC models are more efficient than older ones like Naples.
I’ve been using 4x8GB of B-Die for two and a half years on a single Zen 2 processor, and everything has worked smoothly.
It's tough to run QR since Zen IMC isn't quite as strong as Intel's. The best approach seems to be sticking to the guidelines from the Zen 1 launch: source B-Die from a trusted manufacturer and adjust the DRAM voltage significantly up and down.