A method for managing an external memory of a microprocessor so that the external memory only contains one copy of a common area. By providing an address translator, mapping the page and the address of the common area of the page pointed by a microprocessor to the physical address of the common area of the external memory, using the address translator to translate a page and an address pointed by a microprocessor to a physical address of the external memory, and using the microprocessor to access data stored at the physical address of the external memory; the memory can be more efficiently used.