3
3-5
Working with S5-DOS/ST
C79000-G8576-C760-03
3.2 MS-DOS Memory Manager
A memory manager is a device driver that allows access to or
manages certain types of memory.
MS-DOS (5.0 and 6.2) has the following installable memory
managers:
HIMEM.SYS manages access to the extended memory
EMM386 allows access to the extended memory. It also allows
access to the upper memory blocks (UMBs).
To install a memory manager, use the DEVICE command in your
CONFIG.SYS file. Although memory managers occupy a part of
the conventional user memory, they make up for this by allowing
access to far greater areas of memory in the extended memory or
upper memory area than they themselves occupy.
MS-DOS is usually run in the conventional user memory. This
restricts the conventional user memory available for user
programs. MS-DOS can also be run in the extended memory. In
this case, it uses the 64 Kbytes of the high memory area (HMA).
Since few programs use this area it may prove useful to run
MS-DOS here.
Running MS-DOS in the extended memory area has the following
advantages:
Approximately 40 Kbytes of conventional user memory are
released
It uses the high memory area, part of the extended memory
used by very few programs.
The command DOS=HIGH,UMB specifies the area of the user
memory in which MS-DOS will be located and determines
whether or not upper memory blocks will be used.
Running MS-DOS
in the High
Memory Area
User Memory Management
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