Because from INTEL Core-I series chipset, the memory controller is built in CPU, so each CPU has its own maximu memory size.
And the general memory specification on Sandy Bridge CPU is:
I3, I5 CPU can suppport 8G~16G memory.
I7 CPU can suppport 8G~32G memory.
For more mobile CPU details, please refer to INTEL official website: http://ark.intel.com/
And because there are too many memory brands in the market, in order to prevent the memory compatibility problem, it is recommanded to contact nearest msi service center or dealers to know the exactly memory information that can be installed on your laptop.