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EMM386


Description | Syntax | Parameters | Switches | Related | Notes | Examples | Errorlevels | Availability

Enables or disables EMM386 expanded-memory support on a computer with an 80386 or higher processor. The EMM386 command also enables or disables Weitek coprocessor support. Do not use this command when Windows is running.

The EMM386 device driver, EMM386.EXE, provides expanded-memory support and also provides access to the upper memory area. For information about EMM386.EXE, see EMM386.EXE.


Syntax

EMM386 [ON | OFF | AUTO] [W=ON | OFF]

To display the current status of EMM386 expanded-memory support:

EMM386


Parameters
ON ( | OFF | AUTO v5.0 Win95)
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 only when a program calls for it. The default value is ON.
W=ON ( | OFF v5.0 Win95)
Enables (if set to W=ON) or disables (if set to W=OFF) Weitek coprocessor support. The default value is W=OFF.

Switches

none.


Related

none.


Notes
Installing the EMM386.EXE device driver

To use the EMM386 command, you must have an 80386 or higher processor, and you must also install the EMM386.EXE device driver by using the DEVICE command in your CONFIG.SYS file. If you try to use the EMM386 command on a computer that does not have an 80386 or higher processor, the operating system displays the message:

    EMM386 driver not installed

Reactivating EMM386 expanded-memory support

If EMM386 was loaded when the operating system started but is not currently in use, the ON parameter reactivates expanded-memory support.


Suspending EMM386 expanded-memory support

If EMM386 expanded-memory support is currently active, handle 0 is the only handle allocated, and EMM386 is not providing access to the upper memory area. The OFF parameter suspends EMM386 expanded-memory support. When EMM386 expanded-memory support is off, the EMM386.EXE device-driver header is changed so that programs cannot use expanded memory. This enables you to run non-VCPI-compliant programs such as Win3.0 in Standard mode.


Enabling and disabling Weitek coprocessor support

If the W=ON parameter is specified and the OFF parameter (different from the W=OFF parameter) is not, EMM386 enables Weitek coprocessor support. The high memory area (HMA) must be available to enable Weitek coprocessor support. If you load the operating system into the HMA by specifying DOS=HIGH, you may not be able to enable Weitek coprocessor support.

If you specify the W=ON or W=OFF parameter and no Weitek coprocessor is installed in your computer system, the operating system displays the error message:

    Weitek Coprocessor not installed

Examples

none.


Errorlevels

none.


Availability
External
DOS
v5.0 v5.0A v5.00.02 v5.001A v5.01 v5.02 v6.0 v6.10 v6.2 v6.21 v6.22 v6.23 v7.00 v7.0R1 v7.10 v8.00
Windows
Win95 Win98 WinME
Windows NT
none