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======================================================================
Microsoft(R) Product Support Services Application Note (Text File)
PD0456: HOW DO I GET MS-DOS(R) TO RUN IN THE HIGH MEMORY AREA?
======================================================================
Revision Date: 4/93
No Disk Included
The following information applies to Microsoft MS-DOS versions 5.0 and
6.0.
INTRODUCTION
============
Microsoft MS-DOS can conserve memory by loading itself into the first
64 kilobytes (K) of extended memory, known as the high memory area
(HMA). However, sometimes MS-DOS cannot load into the HMA.
WHAT ARE THE PREREQUISITES FOR LOADING MS-DOS INTO THE HMA?
===========================================================
MS-DOS can load itself into the HMA if all the following conditions
are met:
- Your computer must have an 80286 or higher processor.
- Your computer must have extended memory (MS-DOS cannot load into
expanded memory). Use the MEM command to find out what type of
memory your computer has.
- Your CONFIG.SYS file must contain a DEVICE command for HIMEM.SYS or
an equivalent extended memory manager. (For details, see "What
should I do if MS-DOS won't load into the HMA?" later in this
document.)
- Your CONFIG.SYS file must contain either a DOS=HIGH or DOS=HIGH,
UMB command. The DOS command should appear after the DEVICE command
for HIMEM.SYS, and before any other DEVICE commands. (For details,
see "What should I do if MS-DOS won't load into the HMA?" later in
this document.)
HOW DO I FIND OUT WHETHER MS-DOS HAS SUCCESSFULLY LOADED INTO THE HMA?
======================================================================
To find out whether MS-DOS has loaded into the HMA, type "mem"
(without the quotation marks) at the MS-DOS command prompt.
MS-DOS displays information about your system's memory. If the last
line of the display reads "MS-DOS is resident in the High Memory
Area," MS-DOS has successfully loaded into the HMA.
WHAT SHOULD I DO IF MS-DOS WON'T LOAD INTO THE HMA?
===================================================
If MS-DOS fails to load into the high memory area, follow the
procedures below in order.
Procedure 1: Make Sure Your System Meets
the Prerequisites for Loading MS-DOS into the HMA.
--------------------------------------------------
1. Make sure your system has an 80286 or higher processor.
2. Make sure your computer has extended memory. To find out, type
"mem" (without the quotation marks) at the MS-DOS command prompt.
The MEM command reports the type and amount of memory that your
computer has.
3. Edit your CONFIG.SYS file. To edit the file using MS-DOS Editor,
type the following at the MS-DOS command prompt:
edit c:\config.sys
4. Make sure your CONFIG.SYS file contains a DEVICE command for
HIMEM.SYS. If the file doesn't contain one, insert the following
line at the beginning of the file:
device=c:\dos\himem.sys
5. Make sure your CONFIG.SYS file contains a DOS=HIGH command or a
DOS=HIGH, UMB command. If the file doesn't contain one of these
commands, insert the following line:
dos=high
6. If you're using MS-DOS Editor, choose Exit from the File menu. When
MS-DOS Editor displays a dialog box prompting you to save your
file, choose the Yes button or press ENTER.
7. Restart your computer by pressing CTRL+ALT+DEL.
8. Use the MEM command to find out whether MS-DOS has loaded
successfully into the HMA. If MS-DOS has failed to load into the
HMA, continue with the next procedure.
NOTE: If your MS-DOS directory is on a drive other than C,
substitute the appropriate drive letter for "c" in the above steps
and in the remaining procedures.
Procedure 2: Add the /CPUCLOCK Switch
to the Device Command for HIMEM.SYS.
-------------------------------------
1. Create an MS-DOS startup disk. To do so, insert a formatted
floppy disk in drive A and type the following:
sys c: a:
Notes
- Do not use drive B when you create a startup disk. Most computer
BIOS startup procedures do not look for a disk in drive B when
starting the computer (even though the light on drive B may turn
on momentarily).
- If you are using MS-DOS 6.0, you can skip to step 3. You do not
need to create a startup floppy disk because you can use the
MS-DOS 6 .0 interactive startup key (F8) to bypass commands in
your CONFIG.SYS file if they cause your system to stop responding
(hang). For more information on using interactive startup, see
the "MS-DOS User's Guide and Reference," Chapter 4, "Configuring
Your System."
2. Copy your CONFIG.SYS file to the startup disk by typing the
following:
copy c:\config.sys a:\
3. Use MS-DOS Editor to open your original CONFIG.SYS file. Locate the
DEVICE command for HIMEM.SYS and add the /CPUCLOCK:ON switch to it.
The command should now appear as follows:
device=c:\dos\himem.sys /cpuclock:on
4. Save your CONFIG.SYS file.
5. Restart your computer by pressing CTRL+ALT+DEL.
6. Use the MEM command to find out whether MS-DOS has loaded
successfully into the HMA. If MS-DOS has failed to load into the
HMA, continue with the next procedure.
Procedure 3: Add the /MACHINE Switch
to the Device Command for HIMEM.SYS.
------------------------------------
1. Use MS-DOS Editor to open your CONFIG.SYS file. Locate the DEVICE
command for HIMEM.SYS and add the /MACHINE switch to it. The
/MACHINE switch specifies the type of computer you have. The switch
should be followed by a colon (:) and your machine number (see the
following list). For example, the following DEVICE command
specifies that your computer is a Toshiba(R) 5100 (machine number
7):
device=c:\dos\himem.sys /cpuclock:on /machine:7
The following table lists machine types in alphabetical order, and
shows the corresponding number to specify with the /MACHINE switch:
Machine Type Number
------------------------------------------------
Abacus 386 1
Acer 1100 6
AT&T(R) 6300 Plus 5
Bull Micral 60 16
Chaplet 1
CompuAdd(R) 386 systems 1 or 8
CSS Labs 12
Datamedia 386/486 2
Everex(TM) AT Plus 1800 1
Everex Notebook ELX 1
Excel Computer Systems 13
Hitachi(R) HL500C 8
Hewlett-Packard(R) 14
(HP(R)) Vectra(R)
HP Vectra (A and A+) 4
IBM(R) PC/AT(R) 1, 11, 12, or 13
IBM PS/2(R) 2
Intel(R) 301z or 302 8
JDR 386/33 1
OPT 386-25 motherboard 1
Pak 386SX 1
PC Limited 4
PC 380/33C, PC 350/33C, 2
or PC300/33C BIOS
revision 1.14
Philips 13
Phoenix Cascade BIOS 3, 1, or 8
Toshiba 1600 and 1200XE 7
Toshiba 5100 7
Tulip(R) SX 9
Unisys(R) PowerPort 2
WYSE(R) 12.5 MHz 286 8
Zenith(R) ZBIOS 10
If your computer is not on the list, or you are not sure which
number to use, try machine numbers in the following order: 1, 11,
12, 13, 8, 2-10, 14-16.
2. Save your CONFIG.SYS file.
3. Restart your computer by pressing CTRL+ALT+DEL.
If your computer fails when you restart it, or you see the "ERROR:
Unable to control A20 line!" message, the machine number you
specified is incorrect for your hardware. If the computer hangs and
you are using MS-DOS 5.0, insert the startup disk in drive A and
restart your system. If you are using MS-DOS 6.0, use the F8 key to
start the interactive startup procedure. When you are prompted to
load HIMEM.SYS, press the N key.
Then, edit your CONFIG.SYS file, specify a different machine
number, save your changes, and restart your system. You may need to
try several machine numbers before you identify the one that works
for your computer.
4. After your computer starts, use the MEM command to find out whether
MS-DOS loaded into the HMA. If it did not, repeat this procedure
and specify a different machine number.
ADDITIONAL INFORMATION
======================
If you are using MS-DOS 5.0, refer to the following sources for
additional information:
"Microsoft MS-DOS User's Guide and Reference," page 282, which
explains how to load MS-DOS into the HMA.
"Microsoft MS-DOS User's Guide and Reference," pages 610-613, which
provides details about the HIMEM.SYS device driver.
If you are using MS-DOS 6.0, refer to the following sources for
additional information:
"Microsoft MS-DOS User's Guide," Chapter 6, "Making More
Memory Available"
Microsoft MS-DOS Help Command Reference, (type "help" [without the
quotation marks] at the MS-DOS command prompt).