1. A region descriptor management method, adapted to a device controller of an electronic apparatus, the management method comprising: fetching a plurality of region descriptor entries from a region descriptor table, wherein each of the plurality of region descriptor entries comprises a block initial address and a block length to correspondingly describe a memory block of a memory module; according to the block initial addresses and the block lengths of the plurality of region descriptor entries, combining and adjusting a portion of the plurality of region descriptor entries to be at least one current region descriptor entry; and based on the at least one current region descriptor entry, generating a current region descriptor table, wherein the number of current region descriptor entries in the current region descriptor table is less than the number of region descriptor entries in the region descriptor table.