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Ryzen 7 9800X3D PC Only Posts with One RAM Stick

September 14, 2026 4 answers
Asked by MellowPine47
I'm building a new PC with a Ryzen 7 9800X3D, an MSI PRO X870E-P motherboard, and G.Skill Flare X5 memory purchased as a bundle. The first build would not post with the RAM installed in slots 1 and 3. After removing one stick and moving the remaining stick to slot 2, it posted once, but then stopped posting again. I returned the parts and received replacements, yet I'm experiencing the same behavior. At the moment, the system has posted with a single RAM stick in slot 3, but it previously would not start at all. I've built several PCs before and haven't encountered this issue. Could the memory slots, BIOS support, CMOS settings, or AM5 memory training be the cause?
AM5 Hardware memory training MSI X870E no POST RAM slots Ryzen 9800X3D

Answers

CrispLantern8
For two memory sticks, use the slots recommended in the motherboard manual—typically A2 and B2, which are usually the second and fourth slots from the CPU. Clear the CMOS, install both sticks in those slots, power the system on, and give it time to complete memory training. AM5 systems can take several minutes during the first boot or after changing memory.

MellowPine47: Moving the memory to the recommended slots and clearing the CMOS helped. It posted again.

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SilverKite53
It’s worth confirming that the motherboard BIOS supports the Ryzen 7 9800X3D. A new board will often be compatible, but the manufacturing date and installed firmware still matter. The fact that it reached the BIOS once makes a total compatibility problem less likely, though updating the BIOS may still improve stability.
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AmberOtter71
When troubleshooting, test with one stick in the slot specified for single-module operation, then test the other stick separately. Make sure the modules are fully seated and that the motherboard’s debug LEDs are checked during a failed boot. Once each stick works alone, install both in the proper paired slots and allow extra time for memory training.
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QuietMarble26
Check the motherboard manual carefully for the primary memory slots rather than relying on trial and error. Incorrect slot placement can prevent the system from posting because the memory configuration is connected through the CPU’s memory controller. Also avoid shutting it down too quickly while it is training the RAM.
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