Issue with Disappeared Ram

First off, this isn't my first language and I'm not that tech savvy.
And I hope, this is the right board. Otherwise, feel free to move it where it should belong.

I've run into a problem with my Ram, which seems to be not unheard of. But after searching google and trying every possible fix, I haven't been able to solve it.

I have 4x4GB RAM installed, which Windows and Bios recognized up until recently. Now Bios, Task Manager and the System Details all show 8GB installed, yet CPU-Z show the correct amount. I took out all 4 blades in random order, rearranged them a number of times, everytime with the same result: Only 8GB - with the exception of running only 1 stick, which displays 4GB. CPU-Z always recognized the correct amount, even when I had 3 sticks in, which showed 12GB. I tested it enough to rule out any faulty stick or socket - they seem to be all fine.

I am running W8.1 64x (the same setup when the full 16 were recognized).
I checked if one of the pins of the CPU is bent (it isn't)
There is no max ram checked in msconfig - advanced options.
And since I didn't change any component in the meantime, I can guarantee that motherboard, CPU and RAM are compatible - at least they were a few days ago, so this common issue is ruled out.
Most issues and fixes have to do something with only a certain amount of RAM usable (as stated in the system infos), but otherwise the full amount of RAM at least recognized. This isn't the case here. Only 8GB are seemingly accepted at all.

Heres what CPU-Z show, maybe that helps somehow.


I would appreciate any help or suggestion, since I'm completely out of ideas. I'll do my best to provide any additional info if needed.

What happens if you try one stick at a time? I'm wondering if a stick or two suddenly ceased working; or, if one or two motherboard RAM slots stopped working.

I did some testing in the meantime and found something odd that relates to your question.
One stick only, applying to every of my 4 sticks, works fine and shows the correct amount of GB in the system specs, in GPU-Z and in task manager. It doesn't matter which slot I use. So it SEEMS, that all sticks and all slots are working. This applies to 2 slots/2sticks, in every configuration (dual channel and single channel). As soon as I put 3 in, it all goes downhill. I still get 8GB, but neither CPU-Z nor Task Manager show the correct slots (example: I had slot 1,2 and 4 running, yet 1,2 and 3 were shown).

I testet every stick alone with memtest and they seem to be fine.

Hello there !
Motherboard mark and model?Is there a "memory remap option" in BIOS? If slots and modules are tested and operational,should be a matter of settings...

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