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Memory Optimization 

Introduction to Memory Optimization 

Key Topics 

Goals of Memory Optimization 

Conventional and reserved memory 

Extended and Expanded memory 

Reducing the Load of DOS 

Expanded memory and TSR’s 

Upper Memory Block 

Changes in CONFIG.SYS and AUTOEXEC.BAT 

High Memory Area 

Memory Terminology 

Memmaker.exe file 

Questions 

Memory Optimization

Introduction to Memory Optimization  

The process of memory  optimization is an archaic way of saving several KB’s of memory within a system that has a maximum of 1MB of RAM

Despite advancements in hardware technology and the total memory  limitations being increased to 16MB and above, DOS  could only support 1 MB  of RAM  for backwards compatibility purposes.

Key Topics

  • Reasons for memory  optimization

  • Components of memory

  • Moving TSR’s

  • Changes in CONFIG.SYS  and AUTOEXEC.BAT

  • MEMMAKER.EXE

Goals of Memory Optimization

All programs  inside DOS  must be run in conventional memory

Since the DOS  operating system  also runs in the conventional memory , it drains the conventional memory  of space for applications

In order for DOS  to maximize the total amount of conventional memory  to be used by applications , it must reduce its load on the conventional memory

 

Conventional and reserved memory

As you can see the memory  0KB to 640KB is defined as conventional memory  and is designed to hold DOS  and all DOS applications  by default. The reserved region of the memory is between 640KB to 1024KB.This region is segmented in to 64KB sections designed to run as shadow RAM  for all devices  installed on the system such as the BIOS , VGA  card, etc.

 

Extended  and Expanded memory

Extended  memory  is all the memory above 1MB and can be activated with the HIMEM .SYS  program. Expanded memory  is all the memory above 640KB and can be activated with the EMM386.EXE  program. EMM386.EXE can only activate if the HIMEM.SYS program is activated prior.

 

Reducing the Load of DOS

DOS  reduces its load on the conventional memory  by:-

–Shifting the Terminate and Stay Resident (TSR’s ) programs  from the conventional memory  to the Upper Memory Blocks (UMB ).

–Shifting the transient components of the MSDOS.SYS  file to the High Memory Area (HMA ).

 

Expanded memory  and TSR’s

Expanded memory  is no longer required for most DOS  programs . However we need emm386.exe in a limited capacity to deal with Terminate and Stay Resident TSR’s  programs. TSR’s are programs of DOS that remain in the RAM  after being run and do not release the memory until the computer has been rebooted. We can limit emm386.exe to extend from 640KB to 1MB by using the NOEMS  option of emm386.exe. These changes must be made to the file CONFIG.SYS .

 

 

 

Config.sys

Device = C:\Dos\HIMEM.SYS

Device = C:\Dos\EMM386.EXE noems

DOS=UMB

 

Upper Memory Block

By using the command DOS =UMB  in the Config.sys  file, we are preparing the empty spaces in the reserved memory  block for TSR’s .

 

Changes in CONFIG.SYS  and AUTOEXEC.BAT

 

We can shift the DOS  TSR’s  from the conventional memory  to the Upper Memory Blocks (UMB ) by using the Devicehigh  command in the config.sys file. You could also use the Loadhigh  or LH command in the autoexec.bat file to perform the same task.

 

High Memory Area

By using the DOS =high command inside the config.sys file to shift the transient components of DOS to the High Memory Area (HMA ). The resident components of the DOS operating system  will remain in the Conventional Memory.

 

Memory Terminology

Terminate and Stay Resident (TSR) is a program that remains in memory  once loaded

High Memory Area (HMA ) the first 64KB of RAM  above 1MB

Resident Dos programs  are the components of Dos that must remain in memory  above 0KB

Transient Dos programs  can be shifted to the HMA  by the command DOS =HIGH  

Memmaker.exe file

MEMMAKER.EXE  is a program of DOS  designed to automate the process of memory  optimization.

It asks a series of questions from the user and makes the according amendments in the CONFIG.SYS  and AUTOEXEC.BAT  file for the system memory  to be optimized inside DOS

You can use the command MEM /c to view your systems current memory  distribution.

 

Questions

  1. Which region in the memory  map is the Extended  memory?

  2. Which region in the memory  map is the Expanded memory ?

  3. Which region in the memory  map is the HMA  memory?

  4. Which region in the memory  map is the reserved memory?

  5. Which region in the memory  map is the Conventional memory?

  6. Which region in the memory  map is the UMB  memory?

  7. Which region in the memory  map is the shadow RAM ?

  8. Which region in the memory  map are all DOS  programs  run by default?

  9. How large is the conventional memory

    1. 640KB

    2. 1024KB

    3. 384KB

    4. 64KB

    5. 16MB

  10. How large is the reserved memory

    1. 640KB

    2. 1024KB

    3. 384KB

    4. 64KB

    5. 16MB

  11. How large is the HMA  memory

    1. 640KB

    2. 1024KB

    3. 384KB

    4. 64KB

    5. 16MB

  12. What memory  size will extended memory extend to in a 80286 system

    1. 640KB

    2. 1024KB

    3. 384KB

    4. 64KB

    5. 16MB

  13. What file will activate the extended memory

    1. EMM386.EXE

    2. HIMEM .SYS

    3. TSR

    4. Memory.com

  14. What file will activate the expanded memory

    1. EMM386.EXE

    2. HIMEM .SYS

    3. TSR

    4. CONFIG.SYS

  15. What file will contain all memory  optimization information

    1. EMM386.EXE

    2. HIMEM .SYS

    3. TSR

    4. CONFIG.SYS

Answers

  1. A

  2. B

  3. C

  4. E

  5. D

  6. E

  7. E

  8. D

  9. A

  10. C

  11. D

  12. E

  13. B

  14. A

  15. D

 

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