Under
MS-DOS,
device driver and
TSR modules can take up large amounts of
conventional memory. A memory manager can move some of these into
upper memory blocks or the
High Memory Area, freeing up conventional&memory and creating a larger
TPA. Memory managers also control access to
extended memory, allowing it to be accessed via
XMS, or as
expanded memory via
EMS.
Popular DOS memory mangers include EMM386 and QEMM.