Take a look in the forums, it's full of people trying to mix DRAM from different packages, often the same exact model and having problem after problem. It's at best a 50/50 thing mixing DRAM, a rapshoot, I don't know of a single DRAM or mobo manufacturer (or any competent IT folks) that will advocate mixing packages of DRAM - and I work with many of the mobo and DRAM manufactures as well as networking with lots of IT folks. I spend a lot of time right here in the memory forums helping folks that have tried mixing, and can often get them to play, but there is no guarantees