For the past few days, my system has shown 16 GB of installed RAM but only 8 GB usable, with the other half marked as hardware reserved. This happened once about two years ago and eventually fixed itself after roughly a week. The problem started again after I reseated the memory.
I have tested both DDR4 sticks individually, and each one works normally in either motherboard slot. The issue only appears when both sticks are installed together. With one stick installed, hardware-reserved memory is normal at around 45 MB.
I have already disabled the memory limit in msconfig, reseated and rearranged the RAM, updated Windows, reseated the CPU, checked for bent pins or thermal paste in the socket, reapplied thermal paste, and previously tried clearing CMOS. The system uses an MSI A320M-A PRO motherboard, a Ryzen 5 1600, two 8 GB DDR4 modules, and an RX 5700 XT. What could cause one working memory channel or module to become hardware reserved only when both sticks are installed?
4 Answers
The dedicated GPU is not causing this, and the Ryzen 5 1600 has no integrated graphics that could reserve 8 GB. Also, seeing both modules listed in Task Manager does not prove that all of their memory is usable; the BIOS or firmware may have disabled part of the address space after unsuccessful memory training.
First check how much memory the BIOS reports immediately after POST. If the BIOS sees the full 16 GB but Windows only makes 8 GB usable, the problem may be a Windows configuration issue. If the BIOS itself reports only 8 GB or disables one module, it points more toward memory training, motherboard traces, the CPU's memory controller, or a socket-contact problem.
Since the system is running DDR4, also disable any XMP profile and test at the motherboard's default memory speed. Clear CMOS again now that the issue has returned, then let the board retrain the memory with both sticks installed.
Run several passes of MemTest86 or a memory test in OCCT with both sticks installed. A module can pass when tested alone but fail when the memory controller is operating in dual-channel mode. If the test reports errors, try each stick at default settings and then test them together at a lower speed.
The fact that each stick works by itself does not completely rule out a failing module or a problem with the combined configuration.
This sounds more like a dual-channel or memory-training issue than a graphics-card issue. On this platform, the memory controller is inside the Ryzen CPU, so poor socket contact, a damaged pin, or a marginal CPU memory controller can cause one channel to be disabled while allowing either DIMM to work individually.
Make sure the sticks are installed in the board's recommended paired slots, load BIOS defaults, and check whether the BIOS has a setting such as memory remapping enabled. If the issue persists at stock settings, testing with another known-good matched RAM kit or another compatible CPU would help isolate the motherboard from the processor.
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