Mixing 2 (two) RAMs in dual channel

[Klajdi369]

HI,
So, I have a 4GB DDR3 1333MHZ RAM and im getting another 4GB stick 1333MHZ, I currently have 4 ram slots and 2 channels (1/3, 2/4).
Should I put both rams, and do I put them on slot 1 and 2?

 

[Tradesman1]

No guarantees when mixing DRAM, that said, would pop them in slots 1-3 or 2-4 from CPU which is the norm for dual channel operation - would need to know mobo to be sure

 

[Klajdi369]

No guarantees when mixing DRAM, that said, would pop them in slots 1-3 or 2-4 from CPU which is the norm for dual channel operation - would need to know mobo to be sure

My motherboard is: ASUS M4A89GTD PRO
And actually I dont know which RAM im going to get, I only know its 4GB and 1333MHz.