[ubuntu] Can I combine 2 identical RAM kits?

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http://ubuntuforums.org – I have a mother board that has memory specs of 4 slots and is duel channel, max 4GB per slot and 16GB total RAM. I currently have a 8GB (2x4GB) RAM kit on the board. If I were to buy an an *identical* kit to the 2x4GB kit I have would it be considered "in spec" to put them in and make it 16GB or... (Hardware)