dual channel memory requires you to use 2 sticks of identical memory (same speed, same timings, same size) and runs the memory basicly twice as fast. It doubles the bandwidth the memory has, making 400 Mzh memory effectivly as fast as 800 Mhz memory, which is important with the new P4's that have 800 Mhz FSB as they can run at the same speed so there is no latency.. It is a must with anyone making a high end computer, but keep in mind you have to buy 2 sticks of memory and they have to be identical.