Are the RAM modules you have added of the same kind or they differ? If it is a latency issue you can try swapping the places of the modules. If that doesn't work remove the old RAM and try turning the PC on with a single module of the new RAM on the 1st slot on which the old module was connected.
To check current BIOS version in RUN enter msinfo32. The info is located in system summary. If your BIOS' version begins with P11 that means P11.B3 is what you should install. If it starts with P21, then you should install P21.B4.
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