Q77083 - Optimizing Your Use of Upper Memory Blocks

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Optimizing Your Use of Upper Memory Blocks

The information in this article applies to:

Microsoft MS-DOS operating system version 5.0

SUMMARY

You have set up your computer to load programs or device drivers into upper memory blocks (UMBs). Now you want to make sure you are making optimal use of those UMBs so that you can run as many programs in the upper memory area as possible.

This article provides techniques for making the best use of your computer's upper memory area. To use these techniques, you should be familiar with the information on pages 313-330 of the Microsoft MS-DOS "User's Guide and Reference" for version 5.0, which explains how to load programs into UMBs. In particular, pages 327 and 329 provide some basic information about optimizing your use of UMBs.

This article explains the following optimization techniques:

Starting EMM386 with the NOEMS switch instead of the RAM switch

Finding the best order for loading drivers and programs into UMBs

Adjusting EMM386 to provide more UMBs

STARTING EMM386 WITH THE NOEMS SWITCH INSTEAD OF THE RAM SWITCH

If you do not use programs that require expanded memory (EMS), start EMM386 with the NOEMS switch. Doing so can give you an additional 64K of UMBs, because the NOEMS switch instructs EMM386 not to create an EMS page frame in the upper memory area. If you start EMM386 with the NOEMS switch, programs will be unable to use expanded memory, even when they are running with Windows.

To start EMM386 with the NOEMS switch:

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

Find the DEVICE command that starts EMM386. If the DEVICE command contains the RAM switch, change it so it contains the NOEMS switch instead. The DEVICE command for EMM386 should now look like the following:
device=c:\dos\emm386.exe noems

Save the changes (if any) to your CONFIG.SYS file and quit the text editor. If you are 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 Yes, or press ENTER.

Restart your system by pressing CTRL+ALT+DEL.

After you complete this procedure, some programs might display out-of- memory messages or fail to run. Such programs might require expanded memory. If this is the case, replace the NOEMS switch with the RAM switch to make expanded memory available again.

FINDING THE BEST ORDER FOR LOADING DRIVERS AND PROGRAMS INTO UMBS

When you start a program using the DEVICEHIGH or LOADHIGH commands, MS-DOS loads that program into the largest remaining UMB, even if it would fit into a smaller UMB. Because of this, the order in which you load programs into UMBs is important when trying to optimize your use of the upper memory area. You will need to experiment to find the best order for your system.

Creating a Startup Disk

Before you start optimizing, create a startup floppy disk that contains a backup copy of your CONFIG.SYS and AUTOEXEC.BAT files. To do so, insert a formatted floppy disk into drive A and type the following commands:

sys c: a:
copy c:\config.sys a:\
copy c:\autoexec.bat a:\

Having this startup disk will enable you to experiment more freely; if you change your CONFIG.SYS or AUTOEXEC.BAT file and your computer locks up when you restart it, just insert the backup disk in drive A and press CTRL+ALT+DEL.

Finding the Best Load Order

When loading programs high, MS-DOS loads each program into the largest remaining UMB, even if it would fit into a smaller UMB. Therefore, the order in which you load programs into UMBs is important. In general, when loading programs into the upper memory area, load larger programs before smaller ones. However, this simple load-the-biggest-first method might not always be the most efficient. Sometimes, you might have to juggle the load order to get the most out of the upper memory area.

For example, suppose you want to load the following three programs into UMBs:


   PROGRAM1.EXE   2K

   PROGRAM2.EXE   2K

   PROGRAM3.EXE   3K

Suppose you have two UMBs available; one is 4K in size; the other is 3K in size. (You can find out the sizes of individual UMBs by issuing the MEM /P command. For more information, see page 519 of the "User's Guide and Reference.")

As you can see, PROGRAM3.EXE is the largest, at 3K. If you load PROGRAM3 first, MS-DOS puts it into the largest UMB (4K). Since PROGRAM3 doesn't use the entire 4K of space in that UMB, an additional kilobyte of memory is left unused. The next program, PROGRAM1 (2K), fits into the 3K UMB, again leaving an unused kilobyte of memory. However, PROGRAM2 also needs 2K of contiguous space, and will not fit into either of the 1K UMBs that remain. This is an example of when it's not as efficient to load the largest program first.

A more efficient method would be to load PROGRAM1 (2K), then PROGRAM3 (3K), and then PROGRAM2 (2K). Then, all three programs would fit into UMBs. MS-DOS would load PROGRAM1 into the 4K UMB, leaving 2K of space. PROGRAM3 would then fit into the next largest UMB (3K), and PROGRAM2 would fit into the 2K remaining.

Figuring Out a Program's Memory Requirements

A program's memory requirements determine what size UMB it needs. Unfortunately, it can sometimes be difficult to figure out what size UMB a particular program needs, since this depends on how and when the program allocates memory. In general, programs fall into one of two groups:

Most programs need a UMB that is at least as large as the program's size while it is running.

To find out this size, issue the MEM /C command while the program is running. In most cases, if there is a UMB of that size available, the program should fit into that UMB.

Some programs need a UMB that is at least as large as the program's file size.

Such programs use a lot of memory during startup and require less memory once they are running. Such a program initially needs a large UMB; but, after it has started, the program relinquishes some memory that can then be used to load the next program.

The following table lists some common Microsoft device drivers and memory-resident programs that can run in the upper memory area. The table specifies how to determine the size of UMB that each program needs: by checking the program's size while it is running, or by checking its file size.


   Program Name   Size of UMB It Needs

   ------------------------------------



   ANSI.SYS       File size

   DISPLAY.SYS    Size while running

   DRIVER.SYS     File size

   EGA.SYS        File size

   MOUSE.COM      File size

   MOUSE.SYS      File size

   PRINTER.SYS    Size while running

   RAMDRIVE.SYS   Size while running

   SMARTDRIVE.SYS Size while running

   SETVER.EXE     File size

   APPEND.EXE     Size while running

   ASSIGN.COM     Size while running

   DOSKEY.COM     Size while running

   FASTOPEN.EXE   Size while running

   GRAFTABL.COM   File size

   GRAPHICS.COM   Size while running

   KEYB.COM       File size

   MIRROR.COM     Size while running

   NLSFUNC.EXE    File size

   SHARE.EXE      Size while running

Juggling the Load Order Between Your CONFIG.SYS and AUTOEXEC.BAT Files

Most device drivers are loaded from your CONFIG.SYS file, and most memory-resident programs from your AUTOEXEC.BAT file. MS-DOS processes your CONFIG.SYS file first and then executes the commands in your AUTOEXEC.BAT file. This limits your ability to manipulate the load order of your device drivers and programs, since the device drivers in your CONFIG.SYS file will always load before the programs in your AUTOEXEC.BAT file.

The following tips can help you balance the use of UMBs between device drivers and memory-resident programs:

In your CONFIG.SYS file, start only the largest device drivers using the DEVICEHIGH command. If you use device drivers that are smaller than the largest memory-resident programs that load from your AUTOEXEC.BAT file, start those drivers using the DEVICE command. (Use the DEVICE command to load HIMEM.SYS and EMM386.EXE, since you cannot run these drivers in UMBs.)

In your AUTOEXEC.BAT file, start your largest memory-resident programs using the LOADHIGH command.

If your mouse comes with both a MOUSE.SYS and MOUSE.COM file, you can start your mouse driver from either your CONFIG.SYS or AUTOEXEC.BAT file. This way, you can load the mouse driver at any point in the startup process (as long as you load it after HIMEM.SYS and EMM386.EXE).
- To load the mouse driver into UMBs from your CONFIG.SYS file, use the DEVICEHIGH command to load the MOUSE.SYS file.
- To load the mouse driver into UMBs from your AUTOEXEC.BAT file, use the LOADHIGH command to load the MOUSE.COM file.

ADJUSTING EMM386 TO PROVIDE MORE UMBS

You can adjust EMM386 to allocate additional space in the upper memory area. (This is particularly useful if you have to start EMM386 with the RAM switch to make expanded memory available to programs.) First, carry out the steps in Procedure 1. After carrying out Procedure 1, if you still cannot load programs and device drivers into UMBs, carry out the steps in Procedure 2.

Procedure 1: Including Specific Portions of the Upper Memory Area

Certain addresses in the upper memory area are normally reserved for use by hardware and video drivers; EMM386 does not usually make these areas available as UMBs. However, on many systems, the hardware and video drivers do not use all the reserved memory addresses. The remaining addresses can be included by EMM386 for use as UMBs. To instruct EMM386 to include these unused areas, you use the I switch after the DEVICE command that starts EMM386.

To allocate additional space in the upper memory area for use as UMBs, follow these steps:

Create an MS-DOS startup disk. To do so, insert a formatted floppy disk in drive A and type the following:
sys c: a:

Copy your CONFIG.SYS file to the startup disk by typing the following:
copy c:\config.sys a:\

Edit your original CONFIG.SYS file. To edit the file using MS-DOS Editor, type the following at the command prompt:
edit c:\config.sys

Locate the DEVICE command for EMM386.EXE, and insert the I switch in front of the RAM or NOEMS switch. The I switch specifies a range of addresses in the upper memory area, and tells EMM386 to allocate that memory for use as UMBs. The value you specify for the I switch will depend on your computer and monitor type.
- If your computer is not an IBM PS/2 and does not have a monochrome monitor, add the i=E000-EFFF and the i=B000-B7FF switches before the RAM or NOEMS switch, as follows:
  device=c:\dos\emm386.exe i=E000-EFFF i=B000-B7FF ram
- If your computer is not a PS/2 and has a monochrome monitor, add the i=E000-EFFF switch before the RAM or NOEMS switch, as follows:
  device=c:\dos\emm386.exe i=E000-EFFF ram
- If your computer is an IBM PS/2 and does not have a monochrome monitor, add the i=B000-B7FF switch before the RAM or NOEMS switch, as follows:
  device=c:\dos\emm386.exe i=B000-B7FF ram
- If your computer is an IBM PS/2 with a monochrome monitor, see Procedure 2.

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 Yes, or press ENTER.

Restart your computer by pressing CTRL+ALT+DEL.

If your computer fails when you start it, the memory range you specified for EMM386 is probably being used by hardware or video display drivers. In that case, insert your startup disk in drive A and restart your computer. Then, edit your CONFIG.SYS and remove the I switch(es) you added to the DEVICE command for EMM386. Contact Microsoft Support Services for further assistance.

After your computer starts, check whether your programs loaded into UMBs successfully. To do so, type the following at the command prompt:
mem /c |more
This command displays the contents of your computer's conventional and upper memory, and shows where in memory each program is running. (For more information about the MEM /C command and UMBs, see page 320 of the "User's Guide and Reference.")

Procedure 2: Reducing the Space Set Aside for Use with Expanded Memory

Starting EMM386 with the RAM switch makes fewer upper memory blocks (UMBs) available than starting it with the NOEMS switch. If programs or device drivers do not load into UMBs when your computer starts, there might not be enough UMBs to run those programs. This is because using the RAM switch sets aside 64K of the upper memory area for use with expanded memory. The remaining UMBs might not be large enough to run your programs, even if you were able to include additional addresses by following Procedure 2.

You can instruct EMM386 to set aside 16K of the upper memory area, rather than 64K, for use with expanded memory. This makes more UMBs available, but programs that use expanded memory might run less efficiently. Follow these steps:

Exit from Windows, and type the following at the command prompt:
emm386
EMM386 displays information about its current memory-management activities. Locate the line that reads "Page frame segment" and write down the hexadecimal address on that line. In the following example, the page frame segment is E000.
Page frame segment . . . . . . . . . E000 F

Edit your original CONFIG.SYS file. To edit the file using MS-DOS Editor, type the following at the command prompt:
edit c:\config.sys

Locate the DEVICE command for EMM386.EXE, and insert the P0 switch before the RAM switch. The P0 switch should specify the address you obtained from EMM386 in Step 1. For example, if the page frame segment was E000, the DEVICE command might appear as follows:
device=c:\dos\emm386.exe i=E000-EFFF p0=E000 ram

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 Yes, or press ENTER.

Restart your computer by pressing CTRL+ALT+DEL.

If your computer fails when you start it, insert your startup disk in drive A and restart your computer. Then, edit your CONFIG.SYS file and remove the P0 switch you added to the DEVICE command for EMM386. Then, save the file, restart your computer, and repeat Procedure 2; be sure to check the page frame address carefully.

After your computer starts, check whether your programs were loaded into UMBs successfully. To do so, type the following at the command prompt:
mem /c |more
This command displays the contents of your computer's conventional and upper memory, and shows where in memory each program is running. (For more information about the MEM /C command and UMBs, see page 320 of the "User's Guide and Reference.")

You have solved the problem if your programs and device drivers are running in UMBs.

If your programs and drivers still do not load into UMBs, it is possible that your system simply does not have enough UMBs available to run those programs. See your computer's hardware documentation for information about which addresses in the upper memory area are in use; contact Microsoft Product Support Services for further assistance.

REFERENCES

See the following pages in the "User's Guide and Reference" for additional information:

How to set up your computer to run programs in the upper memory area, pages 313-326

Tips for troubleshooting the process of running programs in the upper memory area, page 327

Information about the DEVICEHIGH command, page 435

Information about the LOADHIGH command, page 518

Information about the MEM command, page 519

Information about EMM386.EXE startup parameters, page 605

Information about HIMEM.SYS startup parameters, page 610

Additional query words: appnote 5.00

Keywords : msdos
Version : MS-DOS:5.0
Platform : MS-DOS
Issue type :
Technology :

Article ID: Q77083

Last Reviewed:
November 9, 1999

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