The Free On-line Dictionary of Computing (30 December 2018):

expanded memory

    Memory used through EMS.  In systems based on
   Intel 80386 or later processor expanded memory is part of
   the extended memory that is mapped into the expanded memory
   page frame by the processor.  The mapping is controlled by
   the EMM.  In earlier systems, a dedicated EMS hardware
   adaptor is needed to map memory into the page frame.  In both
   cases, an appropriate device driver is needed for the proper
   communication between hardware and EMM.

   (1996-01-10)