I added a second kit of the same RAM model to my system, going from two sticks to four. The modules are rated for DDR5-6000 with timings of 30-40-40-96 at 1.4 V. My system uses a Ryzen 7 9800X3D and an ASRock X870 Pro RS WiFi motherboard.
With two sticks installed, the EXPO profile worked normally. After filling all four memory slots, the system now runs around 3600 MT/s with timings near 30-30-30-58. Even after re-enabling EXPO in the BIOS, it falls back to that slower setting. The sticks are identical in model, though they came from two separate kits. Is this expected, and is there a way to run all four at DDR5-6000?
4 Answers
Using all four slots does not automatically make every system slow, but DDR5 platforms are much more sensitive to it than many older DDR4 systems. AMD generally targets two DIMMs at around DDR5-6000 as the ideal configuration, while four-DIMM setups often require reduced frequency or looser settings.
Yes, this is common with DDR5, especially on AMD systems. Four DIMMs put significantly more electrical load on the CPU’s integrated memory controller than two, so a speed like DDR5-6000 may not be stable. The motherboard is likely failing memory training and falling back to a safer setting. Matching model numbers help, but two separate kits are not guaranteed to work together at the advertised EXPO settings.
If you specifically want DDR5-6000, the more reliable solution is usually replacing the four sticks with one matched two-stick kit of the total capacity you need. Two larger DIMMs are generally easier for the memory controller to run than four smaller ones. There is no guarantee that four identical-looking modules from separate kits will reach the same rated speed.
You can try lowering the memory speed manually, such as 5600 or 5200 MT/s, and leave EXPO timings enabled if the BIOS allows it. You may also need to check the motherboard’s memory support list and update the BIOS. Stability matters more than forcing 6000, so test with a proper memory test after each change.
I tried selecting EXPO again, but it still retrains and returns to 3600. Even manually selecting a JEDEC setting seems to end up at the same fallback speed.