Memory oddities

[dst1157]

Having some issues with new memory. My system:

MSI 990FXA-GD80V2 AM3+
AMD FX-8150
G.SKILL Ripjaws 16GB (4 x 4GB) DDR3 1600
EVGA Geforce 670 2GB
Windows 7 64 bit

When I first installed it the BIOS showed 16 GB, but Windows system information showed 16 GB (12 GB usable). I also got a blue screen of death that said I should check my memory, but that has only happened twice, in the last couple weeks. I figured out that's sometimes due to memory not being seated correctly, or faulty memory.

I opened it up, took out each stick, and tried putting them back in one by one to test if any were faulty. Weird thing is that it wouldn't post at all with only one stick installed. It only posts if I have all four sticks installed. (Yes, I put it in the right slot.)

I did that, and the BIOS still says 16 GB, but now Windows says 16 GB (8 GB usable). Somehow I lost one stick, so now I'm down to only two sticks working...

I have a couple questions then:

- Why would the motherboard not post with one stick installed, but it will with all four?
- Why does Windows not want to use all of my RAM, even though it can recognize that it's there?

Thanks for any help.

 

[Engima]

Try to do two RAM sticks and see what happens. It could be that one of the RAM sticks is faulty.

 

[dst1157]

I did try two and three, but I didn't try all combinations of two. I'll give that a shot and see if I can see if there are one or two that are causing problems.