Usually, double-sided is dual bank and single-sided is single bank. Most mobos report the filled banks when you boot. To verify check to see if you see something like: "0, 1" which indicates a single stick of dual bank ram or "0, 2, 3" which indicates one single bank stick in the first slot and one double bank stick in the second slot.
I thought a thought, but the thought I thought wasn't the thought I thought I had thought.