Overview

In the traditional PC architecture that uses the command system of Intel processors, the first megabyte of RAM has a special function. It's no wonder that the first 640 KB of RAM within that first megabyte (which is the only part of memory available for certain types of programs) is known as the conventional (or basic) memory. Part of this memory area is used by system programs; application programs take up the rest. Often, these programs are sensitive to the conventional memory concerns. For example, certain application programs require no less than 600 KB of conventional memory to run. If the amount of available conventional memory is insufficient, such programs will not run, and a message will appear informing you that there is not enough conventional memory. As a matter of fact, this will happen even in a system with a large amount of RAM that exceeds that program's requirements. In the case we are considering, however, this large amount of available RAM is practically useless, because the first 640 KB is the only area that the program can access. This is due to the fact that all memory above the first megabyte is of the extended type, which a normal DOS program can't use.

One of the most common methods of RAM optimization under Windows 9x is using the drivers specially developed for the particular Windows version. These drivers work in protected mode. To maximize conventional memory under Windows 9x, try to avoid if possible using drivers that require an MS-DOS compatibility mode (a real mode). This is because such drivers load in the first MB of memory, thus decreasing the available conventional memory, and resulting in performance degradation and a limited capability of running programs that need a large amount of conventional memory.

To detect realmode drivers under Windows 95, do the following:

1. Click the Start button.

2. From the Start menu select Settings | Control Panel.

3. The Control Panel window will appear. Double-click the System icon.

4. In the System Properties window go to the Performance tab.

A list of real-mode drivers will be displayed. To get additional information on these drivers, click Information (?).

The programs that run under Windows 9x in MS-DOS compatibility mode may require real-mode drivers. To use these drivers, you need to describe them in the appropriate manner in Autoexec.bat and Config.sys files. Real-mode drivers are loaded into conventional memory, and thus decrease the size of available conventional memory. To maximize conventional memory and increase the performance, it's recommended to try loading some of the real-mode drivers into the upper memory area (UMA), which is the upper 384 KB of the first megabyte of system memory, directly above conventional memory. To do this, you must add the following lines to the Config.sys configuration file:

  DOS =HIGH, UMB
  DEVICE=C:\WINDOWS\HIMEM.SYS
  DEVICE=C:\WINDOWS\EMM386.EXE NOEMS HIGHSCAN

Then, in order to load the program in the high memory, you should use the DEVICEHIGH command in Config.sys and LH or LOADHIGH command in Autoexec.bat.

You can also optimize the location of the system programs within the first mega byte of memory and increase the size of conventional memory available for applications using the MemMaker utility specially designed for this purpose. This utility, included with MS-DOS version 6.0 and later versions, modifies the Config.sys and Autoexec.bat configuration files. After you execute MemMaker, device drivers and other resident programs that reside in the RAM will use the conventional memory in the most advantageous manner possible. If possible, MemMaker will try to load resident programs into the so-called UMB blocks. All of this maximizes free space within the conventional memory, thus making it available to user applications, such as, for example, games, educational programs, business applications, multimedia programs, etc.

Note that to run MemMaker, you need a computer that has at least an 80386 (or higher) processor and extended memory. Currently, most computers easily meet this requirement.

Before running MemMaker, do the following:

• Make sure that all the hardware installed in the system (especially the RAM) functions correctly.

• Exit all active programs, such as Windows, MS-DOS Shell, NC, etc.

• Load all the drivers and resident programs which you normally use (including device drivers and software applications).

While loading MemMaker, the user is given the opportunity to choose the mode: Express Setup (standard setup) or Custom Setup.

Later in this chapter we'll consider several aspects that should be taken into account when optimizing conventional memory in order to maximize the amount of available free space. Although the information provided here would be enough to complete this task, it's recommended that you also read the official Microsoft documentation that comes with MS-DOS in order to make your work with MemMaker easier.