Command: jemm386

  JEMM386 is an Expanded Memory Manager.
  JEMM386 has to be loaded in CONFIG.SYS / FDCONFIG.SYS.
  Like other EMMs it installs the following services:
  - Uses extended memory to simulate expanded memory (EMS) according to
    EMS v3.2 and EMS v4.0.
  - Upper memory blocks (UMB) where drivers and resident programs may
    be loaded, thus increasing available free DOS memory.
  - Mapping RAM to the video address segments A000-AFFF and B000-B7FF.
  - VCPI services to allow DOS applications running in V86-mode to
    switch to protected mode. VCPI also implements a simple memory
    management.
  - VDS API to give drivers/applications some control over DMA and
    physical addresses in V86-mode.

Syntax:

  DEVICE=[drive][path][jemm386.exe] [options]
         drive  The drive letter, e.g. C:
         path   The directory, e.g. \example\
  or run it from the command line:
  [drive][path][jemm386.exe] [options]

Options:

 +A20/NOA20     A20-disable emulation on/off (default on).
  ALTBOOT       Use alternate reboot strategy.
  B=segm        Specify lowest segment address for EMS banking
                (default=4000).
  D=n           Set DMA buffer size in KB (default=64, max is 128).
  EMX           Increased EMX DOS extender compatibility.
  FASTBOOT      Fast reboot. Requires Jemm386 to be loaded in CONFIG.SYS.
  FRAME=E000    Set EMS page frame (FRAME=NONE disables frame). Any value
                between 8000 and E000 is accepted, but not all will work.
  I=start-end   Force a region to be used for UMBs. Without this option
                range C000-EFFF is scanned for unused pages. May also
                be used to add (parts of) regions A000-BFFF or F000-F7FF
                as UMBs. Don't use this option if you don't know what
                you are doing!
  I=TEST        Scan ROMs for unused pages, include found regions
                as UMBs.
  [MAX=]=n      Limit for VCPI (and EMS if < 32 MB) memory in KB
                (default 120 MB).
  MIN=n         Reserve up to n KB for EMS/VCPI memory on init
                (default=0).
  NOCHECK       Disallow access to address space without RAM (MMIO)
  NOEMS         Disable EMS handling.
  NODYN         No dynamic XMS memory allocation (use MIN= to set fix
                amount).
  NOHI          Don't move resident part into first UMB.
  NOINVLPG      Don't use INVLPG opcode.
 +PGE/NOPGE     Page Global Enable feature usage on/off (default off).
  RAM/NORAM     Try to supply UMBs on/off (default on).
  S=start-end   Assume Shadow-RAM activated by UMBPCI, include it as UMB.
  SB            SoundBlaster driver compatibility mode.
  SPLIT         Regain partially used EPROM 4 KB pages for UMBs.
 +VCPI/NOVCPI   VCPI Support on/off (default on).
  VDS/NOVDS     Virtual DMA Services on/off (default on).
 +VME/NOVME     V86-Mode Extensions on/off (default off).
  VERBOSE       Display additional details during start (abbr: /V).
  X=start-end   Exclude region from being touched or used by Jemm386.
  X=TEST        Scan memory region C000-EFFF for UMB exclusion.
  /?            Shows the help.

 '+': option can be set dynamically by running Jemm386 from the command
      line.
  When invoked from the command line Jemm386 additionally will understand:
    LOAD        install
    UNLOAD      uninstall

Comments:

  JEMM386 requires a 80386+ CPU. HIMEMX should be loaded before.
  Load JEMM386 as DEVICE=JEMM386.EXE in CONFIG.SYS / FDCONFIG.SYS
  (although it is an ".exe"-file!).
  For more informations see:
    https://github.com/Baron-von-Riedesel/Jemm/tree/master/Html
  OR:
    https://gitlab.com/FreeDOS/base/jemm/-/tree/master/DOC/JEMM
  OR:
    C:\FREEDOS\DOC\JEMM\readme.txt (can be installed with FD live CD).

Examples:

  IN CONFIG.SYS / FDCONFIG.SYS:
    files=20
    buffers=30
    lastdrive=Z
    break=off
    DOS=high,umb
    device=C:\FREEDOS\BIN\himemx.exe
    device=C:\FREEDOS\BIN\jemm386.exe NOEMS
    shellhigh=C:\FREEDOS\BIN\command.com C:\FREEDOS\BIN /E:1024
    /p:C:\fdauto.bat

Command: jemm386

Syntax:

Options:

Comments:

Examples:

See also: