It is probably better to stick with 2G+4G combination, as in that case it is less picky about the correct type of the 4G module (as in, there are modules that w

It is probably better to stick with 2G+4G combination, as in that case it is less picky about the correct type of the 4G module (as in, there are modules that work in this configuration, but not as 2x4G) and IIRC the chipset cannot address the entire 8GB of RAM anyway.