I'm building a system with a Ryzen 7 7800X3D and an ASUS ROG Crosshair X870E Hero. I currently have 32GB made up of two 16GB G.Skill Trident Z5 Neo RGB sticks rated for DDR5-6400 CL32 with EXPO, and I also have a second sealed kit with the exact same specifications. I'd like to reach 64GB for 3D modeling and similar workloads, but I've heard that four DDR5 sticks can be difficult to run at their advertised speeds on AM5. Is it realistic to expect all four sticks to run at 6400MHz, or even around 6000MHz? Would the higher-end motherboard meaningfully improve the chances, or should I sell the second kit and replace the current memory with a 2x32GB kit instead?
3 Answers
If your 3D work genuinely benefits from more than 32GB, adding the second kit can be worth trying. Update the BIOS first, install all four modules, and test with EXPO disabled before gradually increasing the memory speed. Be prepared to run them below their rated speed if necessary. Four-DIMM DDR5 configurations are much more sensitive to BIOS versions, module layout, and the individual CPU’s memory controller.
If you want the least troubleshooting, sell the two 2x16GB kits and buy a single 2x32GB kit listed on the motherboard’s memory support list. A 2x32GB DDR5-6000 kit is much more likely to run at its rated profile than four 16GB modules. If the second kit was purchased some time ago, selling it may also be better financially than returning it, since DDR5 pricing can change substantially.
Four DDR5 DIMMs put significantly more electrical load on the CPU’s integrated memory controller. On AM5, two sticks are generally much easier to run at high speeds, while four sticks often require lower clocks and looser timings. The motherboard can help with signal quality and BIOS support, but it can’t completely overcome the limits of the CPU’s memory controller. You may be able to get 6000MT/s working, but it’s not guaranteed, and 6400MT/s with four DIMMs is unlikely to be plug-and-play. For a reliable 64GB setup, a matched 2x32GB kit is the better option.
That makes sense. I bought the higher-end board hoping its memory design would make four sticks easier, but I guess the CPU’s memory controller is still the main limitation.