I have a six year old R7 with 4 original equipped pc3-12800U 4GB memory modules. System would not POST, only black screen with full power to system, fans running and hard drive activity at initial power on. Originally I suspect the video card but after through testing I discovered it would boot with only one memory module installed in slot 1.

I have tested all 4 chips and computer will boot and run with any of the 4 modules installed in slot 1, but will not POST with any combination of 2 modules installed. Not 1 & 2 slots populated like the manual instructs, not 1 & 3 or 1 & 4. I even tried 3&4 and 2&3 and 2&4. Only with one module in slot 1 will it POST. 

I updated the system BIOS to 11, I also updated the Intel Chipset and the Intel management engine controller.

I have never seen a mother board fail in this manner where one slot functions but the others will not allow boot. Any advise as to possible troubleshooting and finding solution short of buying a refurbished motherboard.