4x4GB installed, only half working (W10, 64 Bit)

[rwbyfeather]

For some reason today when I turned on my PC that I've had for years now, it was slightly sluggish. I updated my video drivers and noticed that Nvidia Geforce Experience reported that I only had 8gb of RAM. I checked my task manager, same thing. I then checked CPU-Z, and it told me I did still have my 16gb installed. Spent some time testing all four of my sticks, same brand, same clock speed, all are DDR3 at 1600Mhz, and each channel is working fine (tested all four individually in each slot), and it detected up to two of my sticks at a time, actually applying the memory, but as soon as I slotted a third into the MOBO, it still only told me I had 8 Gigs (Though when I dug into it, it did register that I had all four DIMM slots filled with 4 gig sticks). I've flashed the latest version of my BIOS onto my MOBO, same thing. I've done the msconfig trick, same thing. Anyone have an idea of what's going on?

Specs:

Motherboard:
Asus CM6870
Processor:
Intel i5-2320
RAM:
ADATA 16gb @ 1600Mhz
Graphics Card:
Nvidia GTX 950 EVGA SC edition

All help is appreciated!

Edit: I've run Memtest and updated W10, and it's still giving me issues. The BIOS still sees the four sticks, but is only allowing me to access 8 Gigs. I am starting to lose hope in recovering this situation.

 

[Lutfij]

Do you have a link to your ram kit? or are they individual sticks of ram? Your platform doesn't have official support for Windows 10. I'd suspect that the OS might've had a corruption in it at some point during an update. You could try and perform a repair install and see if the issue is averted.

 

[rwbyfeather]

Do you have a link to your ram kit? or are they individual sticks of ram? Your platform doesn't have official support for Windows 10. I'd suspect that the OS might've had a corruption in it at some point during an update. You could try and perform a repair install and see if the issue is averted.

Unfortunately I do not, as the RAM came preinstalled in this particular rig when it was purchased. I really don't think repair installing windows 10 will fix it due to the fact that in the BIOS it tells me both that it's only registering 8 Gigs, but that all four are installed and are 4 Gigs each.

 

[rwbyfeather]

Just updating about the situation. I've tried reinstalling W10, I've tried flashing a newer version of my UEFI, and I've tried to manually reinstall the RAM one at a time. If anyone has any other suggestions, I'm all ears.