Dual channel with different sizes?

[rz30]

So how does dual channel work.....

Say you have 4 dimm slots, do you have to use same ram, size, speed and timings in either slots 1 and 3 or in slots 2 or 4 as the only way to enable dual channel?

 

[Pilgrim57]

You want same speed & timings or the fastest will default to the lower setting. Try to stick to same brand. Put largest capacity pair in slots 1 & 3 smaller in 2 & 4. The manual should confirm this.