RAM - Can this configuration support dual channel? I'd like to upgrade my 27" late 2013 iMac. The current 8GB is a bit too little for me, and upgrading all the way to 32GB is a bit too expensive for me at the moment. For the time being, I'd like to upgrade with just one 16GB (2x8GB) kit, with the opportunity to upgrade with another kit later on.

Current configuration:

Channel 0:


empty
4GB


Channel 1:


empty
4GB


8GB total, Each channel has 4GB, therefore dual channel mode is supported.

Desired configuration:

Channel 0:


8GB
4GB


Channel 1:


8GB
4GB


24GB total, each channel has 12GB, but not all chips are the same. Will this configuration support dual channel mode?
Since Mac-tel with 4 slots support dual channel there is no reason this should not work. 

You only have to be careful to have 2 pairs where in each pair the memory modules are the same.