For the past few days, my system has detected both 8 GB DDR4 modules, but only 8 GB is usable and the other half appears as hardware reserved. This happened once before about two years ago and eventually fixed itself after roughly a week. Each stick works by itself in either motherboard slot, but installing both sticks causes the problem. Task Manager shows 16 GB installed with only 8 GB usable, while using one stick results in a normal amount of hardware-reserved memory. I have already disabled the memory limit in system configuration, reseated and rearranged the modules, updated Windows, reseated the CPU, checked for bent pins or thermal paste contamination, and reapplied thermal paste. My system has an MSI A320M-A PRO motherboard, a Ryzen 5 1600, two 8 GB DDR4 sticks, and an RX 5700 XT. What else could cause this, and how can I fix it?
3 Answers
First check how much memory the firmware reports immediately after POST. If the BIOS shows the full 16 GB, the modules are being detected and the issue is probably configuration or memory training in Windows. If the BIOS only reports 8 GB, focus on the motherboard, CPU memory controller, socket contacts, or memory settings instead. Clear CMOS again now, then boot with completely default settings and no memory overclocking profile enabled.
Run several passes of MemTest86+ or a memory test in OCCT with both sticks installed. A module can work by itself but fail when the memory controller has to operate with both channels populated. Also test the sticks at their default JEDEC speed rather than their advertised overclocked speed. If errors appear only with both modules, the problem may be marginal RAM, the CPU's memory controller, or the motherboard's DIMM circuitry.
Since the Ryzen 5 1600 has no integrated graphics, the graphics card is not reserving the missing memory. The fact that both sticks work individually but only half is usable together points more toward dual-channel memory training or a connection problem than a Windows setting. Inspect and clean the DIMM slots, verify the modules are fully latched, and check the CPU socket and motherboard for subtle contact or trace damage. If the BIOS also sees only 8 GB after a CMOS reset, testing with another compatible kit would help isolate the failing component.
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