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No you cannot install firmware from the other variant of the Nokia X3-02, it is technically not possible. The RM-775 variant had a 1GHz processor and double the RAM from memory, but this does not mean that it is made to run exactly the same firmware as its RM-639 brother which you have (running at 680MHz). Ask the same question at your local Nokia Care point and you will receive the same response. From what I can gather, and also other people have asked the same question in the past, but the X3-02 does not support Nokia Maps unfortunately.