the name for the memory remapping feature differs from vendor to vendor. I think memory extension is a similar description for memory remapping, if this was your question!? try to enable it
the relevant name for the feature is written in the manual, if the board supports it. but, some old boards dont support this feature, so you have to investigate by the manufacturer of the board. in this case there might be a chance to flash the bios for enabling the feature. otherwise you have to buy a new board.