Socket LGA1156 CPUs, like socket LGA1366 and AMD processors, have an embedded memory controller. All other Intel CPUs use an external memory controller, which is located on the north bridge chip (a.k.a. MCH or Memory Controller Hub) from the chipset. This means that with other Intel CPUs the chipset (and thus the motherboard) is the component that says what memory technologies and the maximum amount of memory you can have on your PC.
Since now the memory controller is inside the CPU, it is the processor, and not the chipset, that defines the memory technologies and the maximum amount of memory you can have. The motherboard, however, may have a limitation as to how much memory can be installed.
At the moment, the integrated memory controller of socket LGA1156 processors supports only DDR3 memories up to 1,333 MHz under dual-channel architecture, however MSI says P55-GD80 supports DDR3 memories up to 2133 MHz through overclocking. P55-GD80 has four DDR3 sockets and since, at the moment, each DDR3 memory module can have up to 4 GB, you can have up to 16 GB with this motherboard.
The first and the third sockets are dark blue, while the second and the fourth are black. In order to achieve the maximum performance, you should install two or four memory modules to enable the dual-channel architecture. When only two modules are used make sure to install them on the black sockets. If you install them on the dark blue ones the computer won’t turn on.