Here's my system:
Windows 10 64-bit
i5 3570k
AsRock Z77 Extreme3 (bios 1.5)
GTX 760 4GB (Sent in my R9 390 for RMA)
16GB (4GBx4) @ 1600 MHz
128GB SSD 256GB SSD 256GB SSD 1TB HDD
Corsair TX650M
My GPU failed and was sent for RMA, but once I uninstalled AMD drivers for the Nvidia ones, I noticed my PC was only reading 8GB of RAM. After most troubleshooting, I can't seem to find my problem.
Here's what I've tried:
Booting with 1 dimm (boots fine)
Booting with 2 dimms (boots fine)
Booting with 3 dimms (boots while only reading 2 dimms)
Booting with all 4 (either boot loops or boots while only reading 2)
I have tested every possible combo and the boot loop scenarios seem to be random with each dimm. They're all the exact same dual channel kit. I ran memtest and tested each stick individually in each slot, no errors in RAM slots or in memtest. I'm at a loss.
Also did some googling and found one person in some random forum with the same issue, but never posted a fix.