This should help:
Dual Channel DDR structure uses Twin Bank mode, and requires two memory modules plugged into the appointed DIMM slots in order to enable 2 Channel DDR.
There is no such thing as Dual Channel DDR Memory Modules. Regular DDR is installed two modules at a time, each module controlled by a separate channel of the memory controller.
The following data refers to the various ways in which the dual channel controllers are implemented on various motherboards.
To make it easier for users to identify systems with the 2 Channel feature, MSI has considerately chosen to colour the DIMM slots differently to better distinguish them from each other. Take GNB Max for example, the green DIMM1 and DIMM3 are Channel A, while the purple DIMM2 and DIMM4 are Channel B. In order for the user to enable the 2 Channel feature, two memory modules must be plugged in different channels--one in Channel A and another one in Channel B. In the following paragraphs, we will show you the difference between 2 Channel and Single Channel in performance as well as the correct way of integrating 2 Channel memory in the various models of MSI(tm)\'s motherboard.