Dual Channel Different speed ram?

[InTheRightDirection]

Can someone settle this for me?
Mixing RAM, never had a problem yet but on mobo that has 2+ I always keep in separate channels.
I know things will only work at the slowest link in the mix. So ... having say 1 x 4GB DDR3 1066 and 1 x 4GB DDR3 1600.
If it works, the 1600 RAM can only run at the slower speed 1066. That's basic technician knowledge.
However will the two speeds dual channel? I was of the belief you had to have similar speeds, timings and size (preferably a matched set but not mandatory) for a dual channel (not dual data rate, which is not the same thing) I was also of belief that just because 2 modules are in the same channel working, it does not mean it is in a dual channel operation. ie 2x4gb is 8 but not 8gb in dual channel operation. Is that correct?
Further, the second channel usually represented by different color.
A few people have argued with me different although always trying to sell a mismatched stick.
Can anyone knowledgeable weigh in? I consider myself some what knowledgeable and experienced usually, but I am not at like an electrical engineer level.

 

[RememberThe5th]

I've personally ran 2x8GB 1866 and 2x2GB 1333MHz and showed up in dual channel (DDR3 Asus Maximus).

 

[InTheRightDirection]

That is understandable! 1866 is paired with other 1866 not one 1866 paired with one 1333 module. Unless I am misunderstanding you.
I have similar working 2x8 1333, 2x4 1866 in one build

 

[RememberThe5th]

Just to say, you have to match the sizes of the stick and chips (SIngle sided ram and double sided) , since if 8GB is 4 chips on one side vs 8 Chips on both sides, that can cause issues, rather than having same matched Chip sides and unmatched speed (EX. 1866 with 1600) and timings. Since timings will be losen by the motherboard automatic configuration, ex. going from 9-9-9-27-1T to 11-11-11-33 2T and makes things easier.

Only con is by going slower Speed "MHz" and higher timings there is latency, but you can fiddle with that if you want to.

I've only seen instances of DDR2 where i could run 2+1 only, not (by this i mean only 2 ram slots)-> 2+1 1+2 (unmatched single channel or asynchronous mode which motherboard can also do run).

If you can and if you have will and interest into it to figure out will it work, test it out!

Download CPUz and on memory tab will show by Channel # -> Single/Dual/asynchronous