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Q82714: Available Conventional Memory for MS-DOS

Article: Q82714
Product(s): Microsoft Windows 95.x Retail Product
Version(s): WINDOWS:3.0,3.0a,3.1,3.11
Operating System(s): 
Keyword(s): 
Last Modified: 02-OCT-1999

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The information in this article applies to:

- Microsoft Windows versions 3.0, 3.0a, 3.1, 3.11 
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SUMMARY
=======

Running under a system that has very little loaded into conventional memory (a
"bare-bones" system), the Microsoft Windows operating system versions 3.1 and
3.0 operating in enhanced mode will reduce the amount of memory available to
MS-DOS programs by 4K to 16K.

MORE INFORMATION
================

A combination of the following can force Windows in enhanced mode to use more
conventional memory:

- Memory for an MS-DOS virtual machine (VM) must start at a 4K page boundary
  (because of the paging mechanism that the 80386 processor uses.) In the worst
  case, this can cause slightly more than 3K of memory address space to go
  unused.

- Some machines have an additional data area used by the machine's system ROM
  BIOS called the EBIOS data area. This data area usually resides at the top of
  the conventional memory (near the 640K boundary). Because the 80386 paging
  mechanism deals with 4K pages of memory, the EBIOS data area occupies 4K of
  space in Windows in enhanced mode. (Normally, when Windows is not being run,
  the EBIOS area takes up only about 1K of memory because there is no
  limitation of 4K-sized memory pages.)

- When an MS-DOS prompt is started from within Windows, a second copy of the
  MS-DOS command interpreter, COMMAND.COM, is being started. This can account
  for an additional memory loss of 4K.

Additional query words: 3.10 3.00 3.00a 3.0a

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Keywords          :  
Technology        : kbWin3xSearch kbZNotKeyword3 kbWin300 kbWin300a kbWin310 kbWin311
Version           : WINDOWS:3.0,3.0a,3.1,3.11

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