Windows 3.0 Modes and Memory Requirements (58317)


The information in this article applies to:

  • Microsoft Windows 3.0
  • Microsoft Windows 3.0a
This article was previously published under Q58317

SUMMARY

This article contains information on the processor and memory requirements for the three different operating modes of Microsoft Windows version 3.0. These modes are real mode (similar to Windows/286 versions 2.x), 286 standard mode (also known as 286 protected mode), and 386 enhanced mode (also known as 386 protected mode).

MORE INFORMATION

WIN.COM automatically starts up Windows 3.0 in the proper mode for the configuration. However, Windows may be forced into one of the three modes through the following command-line switches: 
   Switch            Mode
   ------            ----

   WIN /R            Real mode
   WIN /S or WIN /2  Standard mode
   WIN /3            Enhanced mode

Notes

  1. All numbers below are approximate and may vary widely depending on the configuration -- for example, Windows device drivers chosen, DOS version, display adapter, etc.
  2. 128K of extended memory is recovered from shadow RAM usage on COMPAQ 386 machines.
  3. Memory requirements take into account memory that can be recovered from SMARTDrive (down to the minimum cache size specified).

Real Mode Requirements

  1. The requirements for WIN.COM to automatically start up in real mode are as follows:

    1. 8088 processor or above
    2. 384K of free conventional memory (393,216 bytes reported by CHKDSK)
  2. The actual real mode requirements are the same as above.

Standard Mode Requirements

  1. The requirements for WIN.COM to automatically start up in standard mode are as follows:

    1. 80286 processor or above
    2. 192K of free extended memory
    3. HIMEM.SYS loaded in the CONFIG.SYS file
  2. The actual standard mode requirements are as follows:

    Standard mode conventional/extended memory requirements are mutually dependent and are not fixed. A typical installation requires a minimum of 128K free at the DOS prompt to run standard mode, assuming sufficient extended memory is free. Standard mode requires between 384K and 512K combined conventional and extended memory to run (approximately).

    For example, if only the minimum 192K of extended memory is free, approximately 322K of conventional is required to run standard mode. However, if available extended is increased to approximately 208K or greater, only 128K of conventional is required. This example is intended to illustrate that the memory requirements are an interrelated, variable issue.

Enhanced Mode Requirements

  1. The requirements for WIN.COM to automatically start up in enhanced mode are as follows:

    1. 80386 processor or above
    2. 1024K of free extended memory
    3. HIMEM.SYS loaded in the CONFIG.SYS file
  2. The actual enhanced mode requirements are as follows:

    See notes for standard mode, above, relating to the interrelationship of conventional/extended requirements. A typical installation requires a minimum of 182K free at the DOS prompt to run enhanced mode, assuming sufficient extended memory is free. Enhanced mode requires between 580K and 624K combined conventional and extended memory to run (approximately).

    Note that enhanced mode is able to start up in low-memory situations only because it provides virtual memory support; although enhanced mode may run in such situations, it may be extremely slow due to the large amount of disk swapping it must perform.
Modification Type:MinorLast Reviewed:7/7/2005
Keywords:KB58317
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