EMM386.EXE

Detailed Command Description

EMM386.EXE

Provides access to the upper memory area and uses extended memory to

simulate expanded memory. This device driver must be loaded by a DEVICE

command in your CONFIG.SYS file and can be used only on computers with an

80386 or higher processor.

EMM386 uses extended memory to simulate expanded memory for programs that

can use expanded memory. EMM386 also makes it possible to load programs and

device drivers into upper memory blocks (UMBs).

Syntax

DEVICE=[drive:][path]EMM386.EXE [ON|OFF|AUTO] [memory] [MIN=size]

[W=ON|W=OFF] [Mx|FRAME=address|/Pmmmm] [Pn=address] [X=mmmm-nnnn]

[I=mmmm-nnnn] [B=address] [L=minXMS] [A=altregs] [H=handles] [D=nnn]

[RAM=mmmm-nnnn] [NOEMS] [NOVCPI] [HIGHSCAN] [VERBOSE] [WIN=mmmm-nnnn]

[NOHI] [ROM=mmmm-nnnn] [NOMOVEXBDA] [ALTBOOT]

Parameters

[drive:][path]

Specifies the location of the EMM386.EXE file.

[ON|OFF|AUTO]

Activates the EMM386 device driver (if set to ON), or suspends the

EMM386 device driver (if set to OFF), or places the EMM386 device driver

in auto mode (if set to AUTO). Auto mode enables expanded-memory support

and upper memory block support only when a program calls for it. The

default value is ON. Use the EMM386 command to change this value after

EMM386 has started.

memory

Specifies the maximum amount of extended memory (in kilobytes) that you

want EMM386 to provide as expanded/Virtual Control Program Interface

(EMS/VCPI) memory. This amount is in addition to the memory used for

UMBs and EMM386 itself. Values for memory are in the range 64 through

the lesser of either 32768 or the amount of extended memory available

when EMM386 is loaded. The default value is the amount of free extended

memory. If you specify the NOEMS switch, the default value is 0. EMM386

rounds the value down to the nearest multiple of 16.

Switches

MIN=size

Specifies the minimum amount of EMS/VCPI memory (in kilobytes) that

EMM386 will provide, if that amount of memory is available. EMM386

reserves this amount of extended memory for use as EMS/VCPI memory when

EMM386 is loaded by the DEVICE=EMM386.EXE command in your CONFIG.SYS

file. EMM386 may be able to provide additional EMS/VCPI memory (up to

the amount specified by the MEMORY parameter) if sufficient XMS memory

is available when a program requests EMS/VCPI memory. Values are in the

range 0 through the value specified by the MEMORY parameter. The default

value is 256. If you specify the NOEMS switch, the default value is 0.

If the value of MIN is greater than the value of MEMORY, EMM386 uses the

value specified by MIN.

W=ON|W=OFF

Enables or disables support for the Weitek coprocessor. The default

setting is W=OFF.

Mx

Specifies the address of the page frame. Valid values for x are in the

range 1 through 14. The following list shows each value and its

associated base address in hexadecimal format:

1 = C000h 8 = DC00h

2 = C400h 9 = E000h

3 = C800h 10 = 8000h

4 = CC00h 11 = 8400h

5 = D000h 12 = 8800h

6 = D400h 13 = 8C00h

7 = D800h 14 = 9000h

Values in the range 10 through 14 should be used only on computers that

have 512K of memory.

FRAME=address

Specifies the page-frame segment base directly. To specify a specific

segment-base address for the page frame, use the FRAME switch and

specify the address you want. Valid values for address are in the ranges

8000h through 9000h and C000h through E000h, in increments of 400h. To

provide expanded memory and disable the page frame, you can specify

FRAME=NONE; however, this may cause some programs that require expanded

memory to work improperly.

/Pmmmm

Specifies the address of the page frame. Valid values for mmmm are in

the ranges 8000h through 9000h and C000h through E000h, in increments of

400h.

Pn=address

Specifies the segment address of a specific page, where n is the number

of the page you are specifying and address is the segment address you

want. Valid values for n are in the range 0 through 255. Valid values

for address are in the ranges 8000h through 9C00h and C000h through

EC00h, in increments of 400h. The addresses for pages 0 through 3 must

be contiguous in order to maintain compatibility with version 3.2 of the

Lotus/Intel/Microsoft Expanded Memory Specification (LIM EMS). If you

use the Mx switch, the FRAME switch, or the /Pmmmm switch, you cannot

specify the addresses for pages 0 through 3 for the /Pmmmm switch.

X=mmmm-nnnn

Prevents EMM386 from using a particular range of segment addresses for

an EMS page or for UMBs. Valid values for mmmm and nnnn are in the range

A000h through FFFFh and are rounded down to the nearest 4-kilobyte

boundary. The X switch takes precedence over the I switch if the two

ranges overlap.

I=mmmm-nnnn

Specifies a range of segment addresses to be used (included) for an EMS

page or for UMBs. Valid values for mmmm and nnnn are in the range A000h

through FFFFh and are rounded down to the nearest 4-kilobyte boundary.

The X switch takes precedence over the I switch if the two ranges

overlap.

B=address

Specifies the lowest segment address available for EMS "banking"

(swapping of 16-kilobyte pages). Valid values are in the range 1000h

through 4000h. The default value is 4000h.

l=minXMS

Ensures that the specified amount (in kilobytes) of extended memory will

still be available after EMM386 is loaded. The default value is 0.

A=altregs

Specifies how many fast alternate register sets (used for multitasking)

you want to allocate to EMM386. Valid values are in the range 0 through

254. The default value is 7. Every alternate register set adds about 200

bytes to the size in memory of EMM386.

H=handles

Specifies how many handles EMM386 can use. Valid values are in the range

2 through 255. The default value is 64.

D=nnn

Specifies how many kilobytes of memory should be reserved for buffered

direct memory access (DMA). Discounting floppy-disk DMA, this value

should reflect the largest DMA transfer that will occur while EMM386 is

active. Valid values for nnn are in the range 16 through 256. The

default value is 32.

RAM=mmmm-nnnn

Specifies a range of segment addresses to be used for UMBs and also

enables EMS support. If you do not specify a range, EMM386 uses all

available adapter space to create UMBs and a page frame for EMS.

NOEMS

Provides access to the upper memory area but prevents access to expanded

memory.

NOVCPI

Disables support for VCPI applications. This switch must be used with

the NOEMS switch. If you specify the NOVCPI switch without specifying

the NOEMS switch, EMM386 does not disable VCPI support. If you specify

both switches, EMM386 disregards the MEMORY parameter and the MIN

switch. Disabling support for VCPI applications reduces the amount of

extended memory allocated.

HIGHSCAN

Specifies that EMM386 use an additional check to determine the

availablity of upper memory for use as UMBs or EMS windows. On some

computers, specifying this switch may have no effect or cause EMM386 to

identify upper memory areas as available when they are not. As a

result, your computer might stop responding.

VERBOSE

Directs EMM386 to display status and error messages while loading. By

default, EMM386 displays messages only if it encounters an error

condition. You can abbreviate VERBOSE as V. (To display status messages

without adding the VERBOSE switch, press and hold the ALT key while

EMM386 starts and loads.)

WIN=mmmm-nnnn

Reserves a specified range of segment addresses for Windows instead of

for EMM386. Valid values for mmmm and nnnn are in the range A000h

through FFFFh and are rounded down to the nearest 4-kilobyte boundary.

The X switch takes precedence over the WIN switch if the two ranges

overlap. The WIN switch takes precedence over the RAM, ROM, and I

switches if their ranges overlap.

[NOHI]

Prevents EMM386 from loading into the upper memory area. Normally, a

portion of EMM386 is loaded into upper memory. Specifying this switch

decreases available conventional memory and increases the upper memory

area available for UMBs.

[ROM=mmmm-nnnn]

Specifies a range of segment addresses that EMM386 uses for shadow

RAM--random-access memory used for read-only memory (ROM). Valid values

for mmmm and nnnn are in the range A000h through FFFFh and are rounded

down to the nearest 4-kilobyte boundary. Specifying this switch may

speed up your system if it does not already have shadow RAM.

[NOMOVEXBDA]

Prevents EMM386 from moving the extended BIOS data from conventional

memory to upper memory.

[ALTBOOT]

Specifies that EMM386 use an alternate handler to restart your computer

when you press CTRL+ALT+DEL. Use this switch only if your computer stops

responding or exhibits other unusual behavior when EMM386 is loaded and

you press CTRL+ALT+DEL.

EMM386.EXE--Notes

Sharing XMS and EMS memory

EMM386 provides EMS/VCPI memory for programs that require it by converting

XMS memory to EMS/VCPI memory. When it is loaded, EMM386 reserves the amount

of memory specified by the MIN switch for use as EMS/VCPI memory (the

default value is 256K). Once this amount of XMS memory is reserved, it is

always available as EMS/VCPI memory and no longer available as XMS memory.

EMM386 may be able to convert additional amounts of XMS memory to EMS/VCPI

memory, up to the amount specified by the MEMORY parameter. EMM386 returns

the additional amount back to XMS memory when it is no longer needed as

EMS/VCPI memory.

If you specify MIN=0, EMM386 does not reserve any XMS memory for use as

EMS/VCPI memory. Instead, it converts XMS memory to EMS/VCPI memory only

when a program requests it. This frees XMS memory when EMS/VCPI memory is

not needed. However, EMM386 will not be able to supply the requested amount

of EMS/VCPI memory if programs have allocated all the XMS memory at the time

of the request.

Must install HIMEM.SYS before EMM386.EXE

You must include a DEVICE command for the HIMEM.SYS device driver in your

CONFIG.SYS file before the DEVICE command for EMM386.EXE.

Using EMM386 memory switches

Unless you want to use EMM386 to provide access to the upper memory area,

you need not specify memory switches on the DEVICE command line. EMM386

usually runs properly with the default values. In some cases, however, you

might want to control how EMM386 uses memory. For example, you can control

where EMM386 puts the EMS page frame or which segments it uses for EMS

pages. You can use as many of these memory switches as you want, in any

order you want.

CAUTION: Use EMM386.EXE parameters carefully. You can make your computer

inoperable if you use them incorrectly.

Using EMM386 to provide access to the upper memory area

In addition to providing access to expanded memory, EMM386 provides access

to the upper memory area, which you can use to load certain programs and

device drivers. You must use either the RAM or NOEMS switch to provide

access to the upper memory area.

To give MS-DOS access to the upper memory area but not to expanded memory,

use the NOEMS switch. To give MS-DOS access to both the upper memory area

and expanded memory, use the RAM switch. The RAM switch provides access to

less of the upper memory area for running device drivers and programs than

does the NOEMS switch. In either case, you must include the DOS=UMB command

in your CONFIG.SYS file. The device command for EMM386.EXE must precede any

DEVICEHIGH commands.

Using EMM386 with Windows 3.1

When EMM386 is used with Windows 3.1, the I, X, NOEMS, Mx, Pnnnn, and FRAME

switches have precedence over the EMMINCLUDE, EMMEXCLUDE, and EMMPAGEFRAME

settings in the Windows SYSTEM.INI file. Changes to these settings in the

SYSTEM.INI file have no effect when EMM386 is loaded.

SMARTDRV double buffering may be required to use EMM386

If you have a small computer system interface (SCSI) or enhanced system

device interface (ESDI) hard disk or other device, you may have to add the

following line to your CONFIG.SYS file:

device=smartdrv.exe /double_buffer

Add the line before any DEVICEHIGH statements and before any statements that

load installable device drivers that use expanded memory. The statement

enables an SCSI or EDSI controller to transfer information to programs that

use the upper memory area or expanded memory.

EMM386.EXE--Examples

To start EMM386 as an expanded-memory emulator, using the default values,

add the following lines to your CONFIG.SYS file:

device=himem.sys

device=emm386.exe

Since no location is specified, MS-DOS searches for the EMM386.EXE file in

the root directory of your startup drive.

To specify that EMM386 allocate a maximum of 4096K of memory and a

guaranteed 256K of memory (the default value), and to specify that the

EMM386.EXE file is located in the DOS directory on drive C, add the

following line to your CONFIG.SYS file:

device=c:\dos\emm386.exe 4096

To emulate expanded memory, specify the segment-base address D000h for the

EMS page frame, and allocate 512K of memory to EMM386, use one of the

following commands:

device=emm386.exe 512 frame=d000

device=emm386.exe 512 p0=d000 p1=d400 p2=d800 p3=dc00

Suppose that, in addition to specifying the conditions set in the preceding

commands, you want to prevent EMM386 from using the segment addresses E000h

through EC00h. To do this and to specify that EMM386 can use 127 handles,

add the following line to your CONFIG.SYS file:

device=emm386.exe 512 frame=d000 x=e000-ec00 h=127

To provide access to the upper memory area but not provide EMS/VCPI memory,

add the following line to your CONFIG.SYS file:

device=emm386.exe noems novcpi

To provide access to the upper memory area and provide EMS/VCPI memory, add

the following line to your CONFIG.SYS file:

device=emm386.exe ram

Contact CustomCodeInc@yahoo.com with comments or questions regarding this site. 
© Copyright, Custom Code,Inc., All rights reserved.