I bought a GA-990FXA-UD3 motherboard on Dec. 22, 2011 and it has been working fine with my 4GB G.Skill RAM kit. I recently purchased an 8GB Mushkin Blackline RAM kit as an upgrade, and that's when the problems started to arise.
SYSTEM:
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CPU: AMD Athlon II X4 640
Motherboard: GA-990FXA-UD3 (rev. 1.1) F6f
RAM: Mushkin Blackline 996995 PC3-12800 8GB (2 x 4GB)
G.Skill Ripjaws F3-12800CL9D-4GBRL 4GB (2 x 2GB)
Graphics Card: Sapphire Radeon 5830
PSU: Corsair HX520W
OS: Windows 7 Professional SP1
The problem is that when I install both sticks of Mushkin RAM, Windows 7 freezes randomly after a short period of time requiring a system reset. My system is fine with the G.Skill RAM kit installed, when only1 stick of Mushkin RAM is installed, or when 1 stick of Mushkin RAM and 1 stick of G.Skill RAM is installed together. All RAM sticks have been tested on my GA-990FXA-UD3 separately in each DIMM without issue. All RAM sticks pass memtest 86+ and Prime95 individually and even when all four are installed together. However, any combination of RAM installed that includes 2 sticks of Mushkin RAM leads to Windows freezing. I never get a BSOD and event viewer doesn't provide any useful information (only that a critical error has taken place because I have been required to do a hard reset). The Mushkin RAM kit can be underclocked down to 800 MHz and the problem doesn't go away. Raising RAM voltage to 1.65V or increasing CPU NB VID only delays the length of time before Windows eventually freezes. With both sticks of Mushkin RAM installed, safe mode freezes before I can reach the desktop screen and Windows installation freezes during file extraction ( no further than 76% extracted).
My Mushkin Blackline 996995 kit has been tested working with no problems on a system using a GA-MA790GPT-UD3H motherboard. I borrowed a Corsair TX750 PSU and replaced my HX520 PSU with it, but that didn't resolve the issue. Flashing my GA-990FXA-UD3 BIOS back to F5 doesn't change anything. Whether the Mushkin RAM kit is operating in single channel or dual channel mode, the freezing in Windows still persists. Disabling startup programs using msconfig doesn't alleviate the problem either.
Any help or advice would be greatly appreciated.