Only half of RAM detected on MSI P55-GD65

[Richard Pieri]

My first guess is that you are running a 32-bit kernel.  A 32-bit Linux kernel can't address more than 4GB.  Try installing a kernel with PAE.

Make sure that the RAM modules all have the same timings and the same power requirements.  The BIOS will detect one module and configure to its specifications which will cause other modules to malfunction.  If the modules aren't all completely identical then stop right here, return the mismatched modules and get replacements that match.

Make sure that the BIOS is set for the correct timings for the modules.  Setting the timings too tight will cause malfunctions.

Make sure that the BIOS is set to provide sufficient power without exceeding the manufacturer's recommendations.  Insufficient power will cause some modules to malfunction.  Excessive power can cause irreparable damage.

--Rich P.