Mixing a 4GB Stick with a 2GB Stick. I need answers fast!

Hybrid7x

Honorable
Oct 30, 2013
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Im about to buy CoD Ghosts but I need more memory since it requires 6GB and I only have 4GB. I decided to mix my 4GB with a new 2GB stick. They are both by Transcend, they are supported by my motherboard and the speed is CL9 on both of them. The question is, is this safe, and would it work? If yes, would it be powerful enough to run CoD Ghosts? And yeah I am a noob :D