COMPUTER INFORMATION

 Understanding low-level memory under Windows 98
Brien M. Posey                                
Mar 23, 2000
In these days of high-level operating systems with graphical 
user interfaces (GUIs), most people assume DOS is dead. This is 
not true, however. Windows 98 rides on top of a version of DOS. 
Even Windows 2000 contains a DOS-like operating system called the 
Recovery Console that you can use for low-level access to the operating 
system. In this article, I'll explain how changes made at the DOS level 
can affect Windows 98. I'll also describe how to optimize these settings. 
Why bother? Right now, you may be wondering why you should even bother 
looking at the DOS settings in Windows 98. After all, Windows 98 was 
designed to function without a Config.sys or Autoexec.bat file. What 
you may not know, however, is that this is only possible because Windows 98
has a Config.sys and Autoexec.bat file built in. These files are 
contained within the boot files. As I'll discuss later, the function 
of these boot files has radically changed since the days of DOS.
The new structure As you may recall, five files were responsible 
for the MS-DOS boot sequence: IO.sys, MSDOS.sys, Command.com, Config.sys, 
and Autoexec.bat. In Windows 98, these files still exist, but they 
have different purposes. In Windows 98, the IO.sys file takes over 
the functions of all the previously mentioned files except for Command.com. 
This doesn't mean you can erase your MSDOS.sys file and expect 
Windows 98 to boot, though. In Windows 98, MSDOS.sys is a text 
file containing user-definable parameters that control how Windows 98 loads. 
As I mentioned, the Windows 98 IO.sys file takes over the functionality
of IO.sys, MSDOS.sys, Config.sys, and Autoexec.bat. The following commands 
are built into the Config.sys portion of IO.sys:
DEVICE=C:\WINDOWS\HIMEM.SYS
DOS=HIGH
DEVICE=C:\WINDOWS\IFSHLP.SYS
FILES=60
LASTDRIVE=Z
STACKS=9,256
BUFFERS=30
SHELL=C:\COMMAND.COM /P
FCBS=4
DEVICE=C:\WINDOWS\SETVER.EXE
Likewise, these commands are built into the Autoexec.bat portion of the IO.sys file:
@ECHO OFF
PATH=C:\C:\WINDOWS;C:\WINDOWS\COMMAND;
PROMPT $P$G
The only reason Windows 98 is able to function without a Config.sys and Autoexec.bat 
file is because it already has one built in. If you don't believe me, or would like 
to see this for yourself, you can. Although you can't easily view the commands 
themselves, you can see the result of them. To do so, rename your Config.sys and 
Autoexec.bat files so that they won't be loaded at boot up. Next, reboot your PC. 
As soon as you see the Starting Windows 98 message, start pounding the F8 key.
You should see the Windows 98 Boot menu. Select the Command Prompt Only command. 
Doing so will load Windows 98 without the GUI. Next, type the following command 
at the command prompt:
MEM /C |MORE
This command displays all files currently loaded into memory. If no Config.sys 
or Autoexec.bat settings were present, you'd see only the basic DOS modules loaded. 
However, this isn't the case. If Windows 98 has a built-in Config.sys and Autoexec.bat, 
you may be wondering why you would ever need one at all. Under normal circumstances, 
you don't have to create custom configuration files. The reason that Microsoft included 
the ability for you to create these custom files is in case the built-in commands are 
insufficient for your needs. For example, by default, Windows 98 sets the
file handles to 60; however, 60 is insufficient for many programs. Therefore, 
you can override the default with a custom setting of perhaps 100, via the 
Config.sys file. Sure, the built-in commands are a nice touch, but you may 
be wondering what good they are if they are often insufficient. The built-in 
commands serve two purposes. First, they guarantee that the operating 
system will always have sufficient resources to load. Second, they make the 
initial setup process much easier for novices. The only reason Windows 98 
even offers a user-configurable Config.sys and Autoexec.bat
file is to offer expansion when the built-in settings aren't enough, and for 
backward compatibility purposes. As you probably know, many hardware components 
and some programs depend on settings found in the Config.sys and 
Autoexec.bat files. For example, suppose that you've been asked to work on an 
older system. If that system contains a legacy sound card, there's a good chance 
that no Windows 98 driver was ever written for it. In such cases, you can often 
load the DOS-based driver. Loading a driver or two may sound trivial, but Windows 98 uses
the same basic memory model as DOS 6.22. Although the operating system as a whole can 
support large amounts of RAM, behind the scenes, it's still that first 640 KB of 
conventional memory that counts. If you have too many drivers to load in the 
Config.sys or Autoexec.bat files, it's entirely possible that you could run 
the system out of memory before Windows even finishes booting. Because 
640 KB is such a small amount of memory to work with, it's important to use it 
wisely. Fortunately, there are some techniques you can use to get the most out of your
conventional memory.

Memory management
If you have commands in your Config.sys or Autoexec.bat file that load external 
drivers, open an MS-DOS Prompt window and type the following command: MEM /C |MORE. 
When you do, you'll see a screen indicating the memory that's accessible to DOS is 
divided into two different types, conventional and upper. Conventional memory, as 
I said earlier, refers to your computer's first 640 KB. Upper memory refers to the 
memory between 640 KB and 1 MB. There's a good chance the upper memory is unused on 
your machine, since upper memory is unavailable to DOS applications by default. 
This means all of your DOS-level drivers are consuming portions of precious 
conventional memory. As you might have guessed, the idea is to move as many of 
these drivers from the conventional memory to upper memory as possible. 
Although it's easy to move some of your drivers to upper memory, it can
be quite a challenge to move enough of them to make any kind of difference. 
Obviously, the first step to optimizing your memory is to enable the upper 
memory if it isn't already enabled. To do so, add the following three lines 
to the top of your Config.sys file (if there are any existing 
commands in your Config.sys file that reference Himem.sys,
 EMM386.exe, or DOS, erase them): 
DEVICE=C:\WINDOWS\HIMEM.SYS
DEVICE=C:\WINDOWS\COMMAND\EMM386.EXE NOEMS
DOS=HIGH,UMB
Once you've added these lines, save the changes to your Config.sys file 
and reboot the computer. When the computer reboots, go to the MS-DOS Prompt 
window and run the MEM /C |MORE command again. This time, you should see the 
upper memory area has been slightly used, although 
your free conventional memory may actually be lower (for now).
Which modules and how much memory?
The next thing you need to do is to make a list of which modules are present 
in memory and their sizes. For example, you'd write down that Himem.sys is 
using 1 KB and that EMM386.exe is using 4 KB. Write down each of the 
modules and how much memory it's using. Once you've compiled this list, 
check out the portion of the screen (after you press a key) 
that tells the size of the largest free upper-memory block and write 
this value down. Once you've compiled all this information, it's time 
to rearrange your memory usage. The first thing you should know is some 
drivers can't run in upper memory. These include things like Himem.sys, EMM386, 
Command.com, and Win.com. Remove these items from your list, since they can't be 
manipulated. You should also be aware the commands that I told you to add 
earlier will automatically add a portion of the SYSTEM to the upper 
memory area. Therefore,  don't try to move the SYSTEM either.
Now that you know what you can't move, look at your list to see 
what you can move. Arrange the items on your list in the order of size 
ranging from largest to smallest. If possible, rearrange the items in your 
Config.sys and Autoexec.bat files to load the larger files first. In the 
Config.sys file, change any DEVICE= commands for the items on your list to 
DEVICEHIGH=. Likewise, add the letters LH to the beginning of commands in 
Autoexec.bat that load files that appear on your list.
At this point, reboot your computer and open an MS-DOS Prompt window. 
Execute the MEM /C |MORE command once more. You should see the conventional 
memory increase and then upper memory decrease. Don't be alarmed if some 
items don't go into upper memory. Earlier I had you write down the size
of the largest free upper memory block. The upper memory is divided into blocks, 
each capable of holding a file. The largest free upper memory block indicates 
the largest file that can be placed in upper memory. For example, if you had 
50 KB of free upper memory with the largest free upper memory block being 19 KB, 
then you wouldn't be able to load anything larger than 19 KB into upper memory. 
The reason I had you to go ahead and try to load everything into upper memory 
regardless of size is some files are capable of fragmenting themselves. 
This means they can reside partially in conventional memory and partially in 
upper memory. As you'll recall, I also had you arrange the commands that load 
your drivers in order of size. I did that so a small file doesn't grab your largest 
free upper memory block, thus making that block inaccessible to other programs. 
However, keep in mind the Config.sys file always executes before the Autoexec.bat file. 
If you're calling a lot of small files in Config.sys, there's a good chance these files 
could eat up all the free upper memory blocks before Autoexec.bat ever executes. 
If you have small drivers in Config.sys and want to leave room in the upper 
memory for a large file in Autoexec.bat, it's best to change the DEVICEHIGH= 
command that precedes the driver to DEVICE=. This will force the smaller files 
to load in conventional memory, leaving more upper memory for your larger files. 
With a little experimenting, you should be able to determine a loading sequence 
that works well, along with the appropriate way to assign programs to conventional 
and upper memory. If you still can't get enough memory If you've manipulated 
everything but still can't seem to get enough memory, remember you'll never free 
up all your conventional memory. However, there is one last hint you might find helpful. 
The BUFFERS command in Config.sys significantly affects your memory. Each buffer 
requires memory. You should determine what the minimum requirements for your 
programs are and set the buffers accordingly. If you're unsure, try removing 
the BUFFERS command completely. As I mentioned earlier, Windows is perfectly 
capable of setting enough buffers automatically 
for the operating system to load.
If you still run a lot of DOS programs or use a lot of 16-bit drivers, 
it's easy to run your computer low on conventional memory. In this article, 
I've discussed ways of manipulating your computer's conventional memory so you 
get the most efficiency. To comment on this article or to share your tips, 
please post a comment below or send us a note.
Brien M. Posey is an MCSE and works as a freelance technical writer and 
as a network engineer for the Department of Defense. If you'd like 
to contact Brien, send him an e-mail. (Because of the large volume of 
e-mail he receives, it's impossible for him to respond to every message. 
However, he does read them all.)