Available Switch Options for Windows NT Boot.ini File

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Article ID: 170756 - View products that this article applies to.
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SUMMARY

When you start Microsoft Windows NT, there are many different switches that can be added to the Boot.ini file that will modify the way Windows NT loads. For additional information about the Boot.ini file, click the article number below to view the article in the Microsoft Knowledge Base:
102873 Boot.ini and ARC Path Naming Conventions and Usage

MORE INFORMATION

The following are the different switches that can be added to the Boot.ini file:

/3GB

Enables user-mode programs to access 3 GB of memory instead of the usual 2 GB that Windows NT normally allocates to user-mode programs. It moves the starting point of kernel memory to 3 GB. This switch is used only in the Windows NT Server Enterprise Edition of Windows NT with Service Pack 3.

For additional information, click the article number below to view the article in the Microsoft Knowledge Base:
171793 Information on Application Use of 4GT RAM Tuning

/BASEVIDEO

The /basevideo switch forces the system into standard 640x480 16-color VGA mode. This is used to enable the system to load if the wrong video resolution or refresh rate had been selected.

For more information, please see the following Microsoft Knowledge Base article:
126690 Windows NT 4.0 Setup Troubleshooting Guide

/BAUDRATE=nnnn

This switch sets baudrate of the debug port. If you do not set the baud rate, the default baud rate is 19,200. 9,600 is the normal rate for remote debugging over a modem. This also enables the /debug switch. For example, /BAUDRATE=9600

For more information on modem configuration, please see the following Microsoft Knowledge Base article:
148954 How to Set Up a Remote Debug Session Using a Modem
For more information on null modem configuration, please see the following Microsoft Knowledge Base article:
151981 How to Set Up a Remote Debug Session Using a Null Modem Cable

/CRASHDEBUG

Enables the COM port for debugging in the event that Windows NT crashes. This enables you to use the COM port for normal operations while Windows NT is running, but converts the port to a debug port if Windows NT crashes (to enable remote debugging).

For more information, please see the following Microsoft Knowledge Base article:
151981 How to Set Up a Remote Debug Session Using a Null Modem Cable

/DEBUG

The /debug switch enables the kernel debugger. This enables live remote debugging of a Windows NT system through the COM ports. Unlike /crashdebug, /debug uses the COM port whether or not you are debugging.

For more information on remote debugging, please see the following Microsoft Knowledge Base article:
121543 Setting Up for Remote Debugging

/DEBUGPORT=comx

The /debugport=comx switch selects a COM port for the debug port (com1, com2, com3...) DEBUGPORT defaults to COM2 if it exists, otherwise it uses COM1. This also enables the /debug switch. For example, /DEBUGPORT=COMx where x is the com port.

For more information, please see the following Microsoft Knowledge Base article:
151981 How to Set Up a Remote Debug Session Using a Null Modem Cable

/HAL=filename

Enables you to define the actual hardware abstraction layer (HAL) to be loaded at startup. This switch is useful in trying out a different HAL before renaming it to hal.dll. This switch is also useful when you want to try booting between multiprocessor and single processor mode when used in conjunction with the /kernel switch. For example, /HAL=halmps.dll this loads the Halmps.dll in the System32 directory.

/KERNEL=filename

The /kernel=filename switch enables you to define the actual KERNEL to be loaded at startup. This is useful in switching between a debug enabled kernel full of debugging code and a regular kernel. It is also useful for forcing Windows NT to load a specific kernel. For example, /KERNEL=ntkrnlmp.exe. This switch command loads the Ntkrnlmp.exe in the System32 directory.

/MAXMEM=nn

The /maxmem=nn switch selects the amount of memory Windows NT detects and can use at startup. This setting should never be set to less than 12. This option is good for checking for bad memory chips. For example, /MAXMEM=12

For more information, please see the following Microsoft Knowledge Base article:
108393 MAXMEM Option in Windows NT Boot.ini File

/NODEBUG

This switch disables the kernel debugger. The switch turns off debugging. This can cause a blue screen if a piece of code has a debug hardcoded breakpoint in its software.

/NOSERIALMICE:comx

This switch disables the mouse port check for this com port. For example, /noserialmice:comx, where X is the number of the serial port. Ports may be separated with commas to disable more than one port. If no serial port is given then all ports are disabled for mouse devices.

This is used with uninterruptible power supply (UPS), like those from American Power Conversion brand (APC), that connects to a serial port. If this option is not available when Windows NT starts, and Windows NT tries to detect a mouse on this port, then the UPS will accidentally start its shutdown mode.

For more information, please see the following Microsoft Knowledge Base article:
131976 How to Disable Detection of Devices on Serial Ports

/NUMPROC=

This switch sets the number of processors that Windows NT will run at startup. This will help test out performance problems and defective CPUs. For example, /NUMPROC=3

/PCILOCK

This switch prevents the HAL from moving anything on the PCI bus. The I/O and Memory resources are to be left exactly as they were set by the BIOS.

For additional information, click the article number below to view the article in the Microsoft Knowledge Base:
148501 Preventing PCI Resource Conflicts on Intel-Based Computers

/SOS

The /sos switch causes the loader to print the name of loaded modules. When Windows NT comes up instead of displaying dots while the devices load, Windows NT will show the actual names of the drivers as they load.

For more information, please see the following Microsoft Knowledge Base article:
99743 Purpose of the BOOT.INI File in Windows 2000 or Windows NT

/ONECPU

This switch is part of Compaq's HAL. The switch tells Windows NT to use only 1 CPU at startup. This will enable you to run a single CPU in a multikernel configuration. For example, /ONECPU.

For more information on other Boot.ini switches that do not relate to Windows NT, please see the following Microsoft Knowledge Base article:
157992 How to Triple Boot to Windows NT, Windows 95/98, and MS-DOS

/WIN95

The /win95 switch loads bootsec.dos.

/WIN95DOS

The /wind95dos switch loads bootsec.w40.

Properties

Article ID: 170756 - Last Review: October 26, 2007 - Revision: 2.2
APPLIES TO
  • Microsoft Windows NT Workstation 3.51
  • Microsoft Windows NT Workstation 4.0 Developer Edition
  • Microsoft Windows NT Server 3.51
  • Microsoft Windows NT Server 4.0 Standard Edition
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