It is NOT necessary to install multiples of RAM in any format, but to have them operate correctly, i.e. Speed and DDR they have to fulfil certain parameters, the best and most reliable way to estabish what will and WILL NOT run in any Mianboard is to go direct to the vendors support website and look it up, they will have listings of RAM they have tested and that will run correctly, also information on the configuration, which slots to use ect. Even so it is suprising what oddities will run quite happily together and also which supposedly compatible RAM, even from Brand names that will not.