Question Windows can't detect all RAM

[Number A]

Hi all,

I recently bought a set of Corsair Vengeance LP CML8GX3M2A1600C9 to add to my alreadt existing set of Corsair Vengeance CMZ8GX3M2A1600C9 for a total of 16GB of RAM.
Both sets are 2x(4GB) DDR3 with a clockspeed of 1600Mhz.

When I check my system information i see that Windows can only detect 12GB of RAM.

When I check Task manager source control I see that slot 1 is empty.

When I run HWinfo I see that my motherboard is currently running in Triple channel BUT it can detect all 4 sticks.

When I check system information I see that windows detects only 12GB of fysical RAM, but it does add up the 16GB of the sticks to the 4GB of Vram from my GPU for a total of 20GB of Virtual memory.

My specs are:
CPU: Intel I7-3820
GPU: GTX 680 Classified 4GB Vram
Motherboard: Rampage IV Formula (has the latest BIOS version of 5001)
PSU: Antec 900W

I also tried both sets seperately in dual channel and then Windows and HWinfo detects them as 8GB, so the sticks are not defect.
And I also tried the 4 sticks in all possible configurations.

Who can help me so Windows detects all 4 sticks?

PS. I'm dutch, which is also the language you see in the images. But I think most of you will be able to understand the relevant data of the images.
If any more information is needed feel free to ask.

 

[rgd1101]

did you test 2 stick on all 4 slot?

 

[Number A]

did you test 2 stick on all 4 slot?

I just tried, and I have found that when I runs dual channel (1-3) Window and HWinfo can detect the 8GB fine.
But when i run dual channel (2-4) Windows can only detect 4GB but HWinfo detects 8GB. Also at (2-4) dual channel Windows detected 4GB of phsyical RAM but 13GB of Vram was available.

Now I placed all 4 sticks back and HWinfo detects quad channel but Windows can still only detect 12GB.

 

[rgd1101]

so the slot doesn't work right

do another test. on 1 stick in 2. see if that boot, then 1 stick in 4 and see if that boot

 

[Number A]

Ok so I just tried 2 and 4 single channel and the PC did't boot when on single channel 4. So it would seem slot 4 is faulty.

But what I don't understand is how HWinfo can still detect the RAM in slot 4 when run in dual channel and quad channel.

 

[Number A]

Little update,

I just ran Memtest and it can detect all 4 sticks but it shows only 12GB of physical RAM is used.

Windows still detects only 12GB and HWinfo still detects 16GB Quad channel...

 

[rgd1101]

detect ram is different then using it.
Could be motherboard or the memory controller(in the cpu) check for bend pin?

 

[Number A]

I just did a CPU reseat and cleaned the socket with compressed air. As far as I could tell there were no bent or misaligned pins.
Unfortunately the reseat didn't show any improvements.

 

[rgd1101]

Got another motherboard/cpu to test?