Memory Musical Chairs

[ZHU92]

I recently re-assembled my gaming rig and popped in my memory (2x8gb Crucial Sport XT) and it would not boot for the life of me. I tried just having one stick in, I've tried moving a single stick into every dimm slot (4), I've tried 2 sticks in and interchanged them between every possible dimm slot combination but no luck. I had a spare 4gb stick of team vulcan laying around so I threw that in and it booted up just fine! I then inserted the crucial memory (both sticks) and it will only boot if there is another stick in there besides the crucial ram. Does anyone know why this is happening or can offer any advice/solution to fixing this? Is my crucial ram bad? I've checked crucial's site and they say the ram is compatible with the motherboard and the crucial ram worked flawlessly before I disassembled my rig. The only changes were the power supply (downgrade from an 800w to a 530w) and the graphics card (downgrade from the an EVGA GTX 660 to an ASUS GTX 650). I even tried to update my drivers and BIOS and that did not help fix/solve the problem.

My motherboard is the MSI 990FXA GD80 AM3+
The ram is:
Crucial Ballistix Sport XT 16GB (2 x 8GB) 240-Pin DDR3 SDRAM DDR3 1866 (PC3 14900) Desktop Memory Model BLS2K8G3D18ADS3
and
Team Vulcan 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 2400 (PC3 19200) Desktop Memory Model TLYD38G2400HC11CDC01

 

[Tradesman1]

Try removing the DRAM, unplug the rig, reset the CMOS, then reinstall one of the 8GB sticks and give it a try

 

[ZHU92]

Sorry for the late reply! I reset the CMOS and it still didnt work, so I underclocked and undervolted the RAM to 1600/1.5v with tighter timings and it works just fine! Even did two 5hr memory tests (memtest, windows) and passed both with no errors. Just weird how it used to run at 1866 and now can only run at 1600. Thank you for the Advice Tradesman1!

 

[Tradesman1]

Now that they are running can prob get back to 1866, by setting freq and timings to spec for 1866, raise DRAM voltage to 1.65 and set the CPU/NB Voltage to 1.35 and give it a try