Real-mode DOS usually only use the memory space below 1M. The basic memory is 640K, while the upper memory requires the corresponding memory manager. The management of basic memory is particularly important because improper use can result in some programs not running. So, how should you optimize the use of it? Here are some suggestions.
First, the memory manager that provides upper memory (UMB) is loaded. There are usually EMM386 and QEMM, but the tools themselves consume a large amount of memory, which is recommended for UMBPCI, a still-evolving tool that provides up to 162K of UMB, and does not occupy basic memory until it is placed in HIMEM. Then, all device driver/TSR are transferred into the UMB (Devicehigh,loadhigh, etc.), so that the remaining basic memory will be high even 630K even if many drivers are loaded (such as the optical drive, mouse, etc.). Note that you try to use a driver that takes up less memory in order to get the most out of UMB.
The following is the memory state information displayed on my Computer (MS-DOS 7.10) with the MEM/A/C command:
Modules using memory below 1 MB:
Type of Memory Total Used free
---------------- ----------- ----------- -----------
Conventional 655,360 10,032 645,328
Upper 163,904 59,152 104,752
Reserved 393,216 393,216 0
Extended (XMS) 49,119,168 82,880 49,036,288
---------------- ----------- ----------- -----------
Total Memory 50,331,648 545,280 49,786,368
Total under 1 MB 819,264 69,184 750,080
Largest executable program size 645,312 (630K)
Largest free upper memory block 103,952 (102K)
Available Memory Area 5,360 (5K)
MS-DOS is resident in the high memory area.
As you can see from the table above, I loaded the following memory-resident programs and drivers:
XMS driver with Himem:dos.
Setver:dos version Table program.
VIDE-CDD: Universal Optical Drive driver. If your optical drive is USB, use Duse.
Cloaking: Memory cloaking API and DPMS driver to save MSCDEX memory footprint.
The IFSHLP:32 bit Disk service program, used in Windows 9x, can not be loaded.
Command:dos command processor.
Killer: Automatically intercept incorrect instructions to prevent panic.
WATCH:TSR Utils is one of the disable commands that can be used to prohibit the functionality of other TSR programs.
MSCDEX: And cloaking program with the MSCDEX, only take up less than 3K of memory, or to account for about 30K.
Doskey:dos with keyboard buffering and history programs.
Ctmouse:dos under the general Mouse driver, accounting for small memory, speed is very fast.
ZENO: Displays the accelerator program.
ESCAPE: At any time you can press the F12 key to return to the DOS mode to prevent panic.
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