Upper Memory
The next 384KB is reserved for I/O device drivers, certain application functions and other
uses. Access to this area is possible only with a special memory driver such as MS-DOS’s
EMM386.EXE driver. By adding the line
dos=umb
to your CONFIG.SYS file, you can load
device drivers and programs into the Upper Memory Block (UMB). Refer to your DOS
documentation for details.
High Memory
The High Memory Area (HMA) is the first 64KB of extended memory (explained below).
You can save some conventional memory by loading the operating system into HMA. If you
are using Toshiba MS-DOS add the line
dos=high
to your CONFIG.SYS file. Refer to your
DOS documentation for details.
Extended Memory
Extended memory is the area on the memory map above 1MB.
Since MS-DOS cannot directly access extended memory, you cannot use it directly to run
MS-DOS programs. However, you can configure all or part of extended memory as
expanded memory. In addition, you can use conventional, expanded and extended memory
as a RAMDRIVE.
The computer uses 192KB of extended memory for Shadow BIOS ROM. When you turn on
your computer, the BIOS copies itself from the flash ROM to the Shadow BIOS area.
Accessing the BIOS from the Shadow BIOS area is much faster than from flash ROM. You
cannot disable Shadow BIOS ROM.
Expanded Memory
Some software packages that run under Toshiba MS-DOS can use memory beyond 640KB
as a work area. These applications were designed according to a standard known as
Expanded Memory Specification (EMS) which was jointly developed by Lotus, Intel, and
Microsoft Corporations. This standard is called LIM-EMS, or expanded memory.
Certain applications require expanded memory to increase their data processing capabilities.
For example Lotus 1-2-3 uses expanded memory to provide more space for large
spreadsheets. A software application designed for LIM-EMS can automatically use the RAM
you assign to expanded memory.
The computer supports LIM-EMS by emulating it in extended memory with the help of the
386 and 486 microprocessor’s special feature, virtual 86 mode.
You do not need any optional hardware devices or hardware settings to support LIM-EMS
