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I have 2 Mac Pros that I need to be at 4GB RAM each, one currently has 6GB with 3x 2GB 1066MHz DDR3 ECC and the other has 3GB with 3x 1GB 1066MHz DDR3.

I know in an ideal world you shouldn't mix sizes and they should all be equal specs but will this be workable and reliable?


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You don't have to mix sizes. You can put 2x2GB in each. In one case, you have to make the 2GB with 2x1GB, but that's not mixing sizes either. – David Schwartz Mar 3 '13 at 5:59

Theoretically, you should be able to mix ECC and Non-ECC DIMMs, and you should be able to mix DIMM sizes...Unless Apple took extra steps to prevent that from working.

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