JEMM386 is an Expanded Memory Manager for an 80386 or above CPU.

JEMM386 is usually loaded in CONFIG.SYS this way:

DEVICE=JEMM386.EXE [options]

You can also load JEMM386 by running it from the command line:

JEMM386.EXE [options]


+A20/NOA20 A20-disable emulation on/off (default on).

ALTBOOT Use alternate reboot strategy.

B=#### Specify lowest segment address for EMS banking (default=4000).

D=### 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=D000-D7FF 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=]##### Limit for VCPI (and EMS if < 32M) memory in kB (default 120 MB).

MIN=##### Reserve up to ##### kB for EMS/VCPI memory on init (default=0).

NOCHECK Disallow access to address space without RAM (MMIO)

NOEMS Disable EMS handling. Use NOEMS to get more free UMBs if you need no EMS.

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=D000-D7FF Assume Shadow-RAM activated by UMBPCI, include it as UMB.

SB SoundBlaster driver compatibility mode.

SPLIT Regain partially used EPROM 4k 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 on).

VERBOSE Display additional details during start (abbr: /V).

X=D000-D7FF Exclude region from being touched or used by Jemm386. X=D000-D7FF can be needed e.g. for some network.

X=TEST Scan memory region C000-EFFF for UMB exclusion.

/? Shows the help.

Options marked with + can also be set dynamically by running JEMM386 from the command line.

When invoked from the command line Jemm386 additionally will understand LOAD to install and UNLOAD to uninstall.