DR-DOS HIMEM

The HIMEM memory manager provides access to the upper memory area. The
features provided by HIMEM, however, will depend on your hardware. If you are
using a 286-based computer with extended memory, the only HIMEM feature you
may be able to use is relocation of the DOS software to high memory. If you
have a chip set or expanded memory board, you can use other HIMEM features.

Use HIMEM if your computer is 80286-based. Also use HIMEM if you are using a
pre-386 machine that has any of the following:

 * A chip set such as Chips and Technologies NeAT* or NeATsx*, LeAPSet* or
   LeAPSetsx*, and SCAT*
 * An EMS or EEMS expanded memory board and driver
 * Permanent upper RAM

NOTE: If you are using a machine with one of the chip sets mentioned above,
HIMEM can only initialize upper memory if you have enabled Shadow RAM and if
Shadow RAM is available. Your machine's hardware setup program, which is
normally invoked by a special keyboard sequence during reset, enables Shadow
RAM. However, the setup program usually allows you to move ROM into RAM as
well; ensure that you leave Shadow RAM available for HIMEM. Otherwise, the
only HIMEM feature you will be able to use is the relocation of the operating
system software to high memory.

HIMEM is loaded and configured by a DEVICE statement in the CONFIG.SYS file.
This statement is automatically placed in CONFIG.SYS when you choose to load
the 80286 memory manager during SETUP (or INSTALL). The configuration of HIMEM
depends on the values you set in SETUP and on changes you make yourself to
CONFIG.SYS.

The full syntax of the HIMEM DEVICE statement is as follows:

DEVICE = C:\DRDOS\HIMEM.SYS

[/CHIPSET=AUTO|chipset|NONE]

[/EXCLUDE=start-end[,start-end]...]

[/INCLUDE=start-end[,start-end]...]

[/ROM=start-end[,start-end]...|AUTO|NONE]

[/USE=start-end] [/VIDEO[=[start-]end]] [/XBDA]

The following table describes the HIMEM options.


/CHIPSET=AUTO|chipset|NONE

HIMEM automatically detects the type of chip set on your computer (or EMS or
permanent upper RAM). If the chip set or memory type is supported, HIMEM maps
Shadow RAM into upper memory accordingly. You can use the CHIPSET option,
however, when you experience difficulty mapping Shadow RAM or if you want to
prevent mapping. See the complete list of the values you can specify for
chipset below.

AUTO (the default) allows HIMEM to determine the chip set or memory type
automatically. NONE disables mapping of Shadow RAM.

Value    Explanation

AM286ZX  For Advanced Micro Devices Am286ZX/LX chip set.

EMSALL   For all EMS upper memory, including the page frame. This option
         disables use of EMS by all other programs.

EMSUMB   For EMS 4.0 or EEMS upper memory blocks. An EMS 4.0 or EEMS memory
         manager must also be loaded before HIMEM.

HEDAKA   For Ever-Success HEDAKA D60 chipset.

NEAT     For Chips and Technologies NeAT, NeATsx, LeAPSet, or LeAPSetsx chip
         set.

RAM      For permanent upper RAM. You must also use the /USE option to define
         the location of the RAM to HIMEM.

SCAT     For Chips and Technologies SCAT chip set.


/EXCLUDE=start-end[,start-end]...

Forces the memory manager to exclude the specified areas of upper memory when
it searches for usable memory; start and end are the starting and ending
segment addresses of each area to exclude.


/INCLUDE=start-end[,start-end]...

Tells the memory manager to test the specified areas of upper memory when it
searches for usable memory; start and end are the starting and ending segment
addresses of each area to include.


/ROM=start-end | AUTO | NONE

Copies slow Read-Only Memory (ROM) into fast Random Access Memory (RAM); start
and end specify the starting and ending segment addresses of an area of ROM to
copy, AUTO copies all slow ROM to RAM, and NONE disables copying.


/USE=start-end[[,start-end]...]

Forces the memory manager to use a specified area of upper memory when it
searches for usable memory; start and end are the starting and ending segment
addresses of the area to use.
NOTE: Because USE can map RAM over any hardware or ROM present in the
specified memory area, you should not use it unless you are very experienced
in allocating upper memory. Also, use conditional statements when you
experiment with USE in CONFIG.SYS or have a bootable diskette available
containing copies of your original CONFIG.SYS and AUTOEXEC.BAT files, in case
you encounter problems.


/VIDEO[=[start-]end]

Makes unused video memory space available to applications when all the video
memory is not being used by the video display adapter. Video memory (the upper
memory immediately above 640 KB) is normally reserved for use by the video
display adapter.


/XBDA

Keeps the extended BIOS data area (XBDA) at the top of conventional memory,
for applications that require it to be there. If you enable sharing of video
memory (/VIDEO), the memory manager automatically moves the XBDA to the bottom
of conventional memory to allow contiguous memory.
