2 versus 4 DDR5 RAM sticks on a 7800X3D motherboard
2 versus 4 DDR5 RAM sticks on a 7800X3D motherboard
There appear to be significant problems with employing four DDR5 sticks, though this isn't universal. I've noticed enough discussions to advise caution around this configuration.
It’s best to use two sticks unless your memory needs go beyond what two can handle. Regarding latency, the situation isn’t straightforward. However, having two sticks usually eases the load on the CPU’s memory controller, allowing you to reach full XMP performance or even boost it further yourself. Overclocking might involve either higher speeds or reduced latency.
To explain this further: Adding more RAM DIMMs within a memory channel doesn't boost bandwidth. Bandwidth depends on the CPU's supported channels and types. For instance, in Ryzen 7000 series systems, you have two memory channels. To achieve peak performance, use one high-performance DIMM per channel. Having more than one DIMM per channel actually lowers overall speed due to higher access delays. Also, DDR5 RAM has faced stability problems when using more than one DIMM per channel since its release, though improvements are being made. It remains a risky choice.
This boosts bandwidth by adding more ranks, though it slightly increases latency. The decision depends on memory type and application needs. I use Quad Rank DDR4 (four 16GB sticks), which gives a noticeable speed gain with only a minor latency cost. Micron E-die limits help reduce timing constraints even with just two sticks. On Zen 5000 series and below, keeping FCLK and MEMCLK in sync is essential for quad rank benefits, as higher RAM speeds are less effective without proper synchronization. In contrast, the 7000 series allows pushing RAM higher because it doesn’t require strict FCLK alignment, making dual-rank setups more advantageous. Overall, using two dual-rank sticks provides a solid performance lift without excessive strain, while quad ranks offer a trade-off between speed and controller load.
The discussion shifts toward meaning. The difference between single and dual-rank RAM doesn't alter the memory channel's bandwidth, but affects how effectively the RAM stick and CPU memory controller collaborate to fill the channel. As you noted, smaller MTU and tighter timings make DIMM ranks less critical overall. This can be seen as another method to boost channel utilization. Still, acknowledging your point about real-world performance, in most cases—except extreme overclocking—the presence of dual-rank RAM generally improves speed, especially for DDR4 systems. For DDR5, a reference exists here: https://www.anandtech.com/show/17269/ddr...ers-matter. Testing confirms that using one DIMM per channel, paired with the highest compatible RAM, yields optimal results. In practice, a straightforward recommendation to seek dual-rank RAM would have been clear enough for clarity.
I've noticed and heard about it too, but I've also seen people improving over time once their memory training started regularly. If things don't go well, I'll keep those extra sticks ready for an ITX build or something similar for learning.
I'm all about learning and that's true! I actually like wanting to run four sticks mostly for style, but I also need the RAM because I've been thinking about doing some video editing work. If I manage to get four sticks, I'd probably notice a slight slowdown, but if pure performance is my goal, sticking with two sticks of the RAM I mentioned would be better.
I definitely understand the appeal of a 4 DIMM look! It makes sense, and I've experienced it before. However, it's wise to be aware of the compromises involved. Currently, there aren't many 4 DIMM kits for DDR5 RAM available, especially not from major manufacturers. Purchasing two separate kits of two DIMMs each carries some risk—you might achieve the advertised speed, like 6000mtu, or worse, end up with a lower performance level such as 4800mtu or even system incompatibility at 5200 or 5600mtu. Most likely, you'll settle for something in between.