Running Both Extended and Expanded Memory on Your Computer (96766)


The information in this article applies to:

  • Microsoft MS-DOS operating system 5.0
  • Microsoft MS-DOS operating system 5.0a
  • Microsoft MS-DOS operating system 6.0
  • Microsoft MS-DOS operating system 6.2
  • Microsoft MS-DOS operating system 6.21
  • Microsoft MS-DOS operating system 6.22
This article was previously published under Q96766

SUMMARY

This article explains how to allocate memory and set up your system to run both expanded and extended memory. Some applications require expanded memory and others need extended memory. As a result, you may decide to customize your system. For example, you may want to run MS-DOS in the high memory area (which is part of extended memory) while also running applications in expanded memory. As a result, you may want to allocate your memory so that your system runs more efficiently.

The method you use to allocate memory differs depending on the type of computer you have. Refer to the section that applies to your computer's processor.

80386 AND 80486 SYSTEMS

If your computer has an 80386 or 80486 processor, it supports both expanded and extended memory. Most 80386 and 80486 computers come with 1 megabyte (MB) or more of extended memory. The EMM386.EXE device driver, which comes with MS-DOS, can use a portion of your computer's extended memory to emulate expanded memory. Applications that need expanded memory can get it from EMM386.EXE, while other applications can still use the remaining extended memory.

MS-DOS 6.0 or 6.2

If you have MS-DOS 6.0 or 6.2, you can run MemMaker to configure your 80386 or 80486 system to provide both extended and expanded memory. To do so, type the following at the MS-DOS command prompt:

memmaker

When MemMaker asks you if you want expanded memory, choose Yes. You can then accept the default settings and let MemMaker configure your computer's memory.

MS-DOS 5.0

If you have MS-DOS 5.0 Upgrade, do the following:

  1. If your memory board can be configured as expanded or extended memory, configure the board so that it provides only extended memory. (To reconfigure your memory board, see the documentation that came with your board or contact your hardware vendor.)
  2. Create an MS-DOS startup disk by inserting a formatted floppy disk in drive A and typing the following at the MS-DOS command prompt and pressing ENTER

    sys <drive>: a:

    where <drive> is the drive where your CONFIG.SYS file resides. For example, if your CONFIG.SYS file is located on drive C, type the following command:

    sys c: a:

  3. Copy your CONFIG.SYS file to the startup disk by typing the following at the MS-DOS command prompt and pressing ENTER

    copy <drive>:\config.sys a:\

    where <drive> is the drive where the CONFIG.SYS file currently resides.

    For example, if your CONFIG.SYS file is located on drive C, type the following command:

    copy c:\config.sys a:\

    If, after you complete these steps, your computer fails to start normally or you have any other problems, you can use the startup disk to start your system and restore your original configuration. To get your system running again, insert the startup floppy disk into drive A and restart your system. Then, copy your backup CONFIG.SYS file to the drive on your system where the original CONFIG.SYS file resided by typing the following command

    copy a:\config.sys <destination>

    where <destination> is the drive on your system where the original CONFIG.SYS file resided (usually drive C). For example, if your original CONFIG.SYS file was on drive C, type the following command:

    copy a:\config.sys c:\

  4. Edit your original CONFIG.SYS file. To edit the file using MS-DOS Editor, type the following at the MS-DOS command prompt and press ENTER

    edit <drive>:\config.sys

    where <drive> is the drive where your CONFIG.SYS file currently resides. For example, if CONFIG.SYS is located on drive C, type the following command:

    edit c:\config.sys

  5. Make sure your CONFIG.SYS file contains a DEVICE command for HIMEM.SYS. The command should appear before any other DEVICE commands and should look like the following

    device=<path>\himem.sys

    where <path> is the drive and directory where your HIMEM.SYS file currently resides. For example, if your HIMEM.SYS file is located in your DOS directory on drive C, type the following command:

    device=c:\dos\himem.sys

  6. Add a DEVICE command for EMM386.EXE that has the location of EMM386.EXE, that specifies you want EMM386.EXE to emulate expanded memory, and that indicates the amount of extended memory to allocate to EMM386.EXE. The following DEVICE command specifies that EMM386.EXE should use 640 kilobytes (K) of extended memory to emulate expanded memory

    device=<path>\emm386.exe 640

    where <path> is the drive and directory where your EMM386.EXE file currently resides. For example, if your EMM386.EXE file is located in your DOS directory on drive C, type the following command:

    device=c:\dos\emm386.exe 640

    If you also want to run programs in the upper memory area to increase your available conventional memory, add the RAM switch to the DEVICE command. The following command specifies that EMM386.EXE should provide 640K of emulated expanded memory, and should also provide access to upper memory blocks (UMBs)

    device=<path>\emm386.exe 640 ram

    where <path> is the drive and directory where your EMM386.EXE file currently resides. For example, if your EMM386.EXE file is located in your DOS directory on drive C, type the following command:

    device=c:\dos\emm386.exe 640 ram

    NOTE: Do not use the NOEMS switch; the NOEMS switch disables all support for expanded memory.
  7. If you want MS-DOS to reside in the high memory area, make sure your CONFIG.SYS file contains a DOS=HIGH command (or a DOS=HIGH,UMB command if you used the RAM switch with EMM386.EXE). If the file doesn't contain one of these commands, insert the following line after the DEVICE=<path>\HIMEM.SYS command:

    dos=high,umb

  8. Close MS-DOS Editor by choosing Exit from the File menu, and save the new CONFIG.SYS file by choosing Yes or pressing ENTER when MS-DOS Editor displays a dialog box prompting you to save your file.
  9. Restart your computer by pressing CTRL+ALT+DEL.
  10. Use the MEM command to check that both expanded and extended memory are available. (For information about interpreting output from the MEM command, see pages 519-522 of the Microsoft MS-DOS 5.0 "User's Guide and Reference.")

Example

Suppose your HIMEM.SYS, EMM386.EXE, and SMARTDRV.SYS files are in the DOS directory on drive C and you have an 80386 computer with 2 MB of extended memory that you want to configure as follows:

  • 512K of expanded memory for your word processing application
  • 1024K of extended memory for SMARTDrive
  • Maximize conventional memory
Your CONFIG.SYS file would contain the following commands: 
   device=c:\dos\himem.sys
   device=c:\dos\emm386.exe 512 ram
   dos=high,umb
   devicehigh=c:\dos\smartdrv.sys 1024
The first DEVICE command loads HIMEM.SYS, which provides access to extended memory. The next DEVICE command loads EMM386.EXE, which provides 512K of expanded memory for your word processor. The RAM switch instructs EMM386.EXE to also provide access to the upper memory area. The DOS command loads MS-DOS into the high memory area and specifies that you want to be able to load programs into the UMBs. The DEVICEHIGH command loads SMARTDrive into the upper memory area and creates a 1024K cache in extended memory. With this CONFIG.SYS file, there should be about 512K of extended memory left over.

80286 SYSTEMS

If your computer has an 80286 processor, it supports both expanded and extended memory. Many 80286 computers have 384K of built-in extended memory. Others have an add-in memory board. Add-in memory boards can contain expanded or extended memory.

If your 80286 computer has an add-in memory board, you might be able to configure the memory board so that it provides both expanded and extended memory. For information about configuring your memory board, see the documentation that came with the board or contact your hardware vendor.

If your computer's memory board can provide both expanded and extended memory, follow these steps:

  1. Configure your memory board so that it provides as much expanded memory as your application requires. (See your application's documentation for information about its memory requirements.) Leave any remaining memory as extended.
  2. Create an MS-DOS startup disk by inserting a formatted floppy disk in drive A and typing the following at the MS-DOS command prompt

    sys <drive>: a:

    where <drive> is the drive where your CONFIG.SYS file currently resides. For example, if your CONFIG.SYS file is located on drive C, type the following command:

    sys c: a:

  3. Copy your CONFIG.SYS file to the startup disk by typing the following at the MS-DOS command prompt and pressing ENTER

    copy <drive>:\config.sys a:\

    where <drive> is the drive where the CONFIG.SYS file currently resides. For example, if your CONFIG.SYS file is located on drive C, type the following command:

    copy c:\config.sys a:\

    If, after you complete these steps, your computer fails to start normally or you have any other problems, you can use the startup disk to start your system and restore your original configuration. To get your system running again, insert the startup floppy disk into drive A and restart your system. Then, copy your backup CONFIG.SYS file to the drive on your system where the original CONFIG.SYS file resided by typing the following command

    copy a:\config.sys <destination>

    where <destination> is the drive on your system where the original CONFIG.SYS file resided (usually drive C). For example, if your original CONFIG.SYS file was on drive C, type the following command:

    copy a:\config.sys c:\

  4. Edit your original CONFIG.SYS file. To edit the file using MS-DOS Editor, type the following at the MS-DOS command prompt

    edit <drive>:\config.sys

    where <drive> is the drive where your CONFIG.SYS file currently resides. For example, if your CONFIG.SYS file is located on drive C, type the following command:

    edit c:\config.sys

  5. Make sure your CONFIG.SYS file contains a DEVICE command for your memory board's memory manager. The command should appear before the DEVICE command for HIMEM.SYS. (See your memory board's documentation for information about installing its memory manager.)
  6. Make sure your CONFIG.SYS file contains a DEVICE command for HIMEM.SYS. The command should appear after the DEVICE command for your memory board's device driver, but before any other DEVICE commands. The DEVICE command for HIMEM.SYS should look like the following

    device=<path>\himem.sys

    where <path> is the drive and directory where your HIMEM.SYS file currently resides. For example, if your HIMEM.SYS file is located in your DOS directory on drive C, type the following command:

    device=c:\dos\himem.sys

  7. If you want MS-DOS to load itself into the high memory area, make sure your CONFIG.SYS file contains a DOS=HIGH command. If the file doesn't contain this command, insert the following after the DEVICE=<path>\HIMEM.SYS command:

    dos=high

  8. Close MS-DOS Editor by choosing Exit from the File menu, and save your file by choosing Yes or pressing ENTER when MS-DOS Editor displays a dialog box prompting you to save your file.
  9. Restart your computer by pressing CTRL+ALT+DEL.

    If your computer fails when you restart it, your expanded memory manager might be incompatible with HIMEM.SYS. To get your system running again, insert the startup floppy disk into drive A and restart your system. Then, copy your backup CONFIG.SYS file to the drive on your system where the original CONFIG.SYS file resided by typing the following

    copy a:\config.sys <destination>

    where <destination> is the drive on your system here the original CONFIG.SYS file resided (usually drive C).

    For example, if, in step 3, your original CONFIG.SYS file was on drive C, type the following at the MS-DOS command prompt:

    copy a:\config.sys c:\

    For help in getting your expanded memory manager to work with HIMEM.SYS, contact Microsoft Product Support Services or the manufacturer of your expanded memory board.
  10. Use the MEM command to make sure that both expanded and extended memory are available. For information about interpreting output from the MEM command, see pages 519-522 of the Microsoft MS-DOS 5.0 "User's Guide and Reference" or type help mem at any MS-DOS 6.0 command prompt.

8086 OR 8088 SYSTEMS

If your computer has an 8086 or 8088 processor, you can use expanded memory only. The 8086 and the 8088 processors do not support extended memory. To set up your computer so that applications can use the memory on your expanded memory board, see the documentation that came with your memory board.

REFERENCES

MS-DOS 5.0

For additional information, see the following pages in the "User's Guide and Reference" for version 5.0:

  • An overview of memory concepts, page 274
  • Information about installing HIMEM.SYS, page 279
  • Information about using EMM386.EXE as an expanded memory emulator, page 289
  • Information about the DEVICE command, page 433
  • Information about the MEM command, page 519
  • Details about EMM386.EXE startup parameters, page 605

Versions 6.0 and 6.2

For more information, see the following sources:

  • Information about making more memory available, Chapter 6 in the "User's Guide" for versions 6.0 and 6.2.
  • Information about the DEVICEHIGH, LOADHIGH, and MEMMAKER commands, Help (type help at any MS-DOS command prompt).
  • Information about EMM386.EXE or HIMEM.SYS, Help (type help at any MS-DOS command prompt).
Modification Type:MajorLast Reviewed:5/12/2003
Keywords:KB96766
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