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Q68805: How to Reboot Your Machine Within a MASM Application

Article: Q68805
Product(s): Microsoft Macro Assembler
Version(s): 5.0,5.1,5.1a,6.0,6.0a,6.0b
Operating System(s): 
Keyword(s): 
Last Modified: 06-MAY-2001

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The information in this article applies to:

- Microsoft Macro Assembler (MASM), versions 5.0, 5.1, 5.1a, 6.0, 6.0a, 6.0b 
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SUMMARY
=======

You can perform a complete reboot (cold boot) on an 8086-based machine by
jumping to the address FFFF:0000. This action also reboots many 80286 and 80386
machines. The address contains a jump instruction that leads to the machine's
initialization code. For this method to succeed, your machine must be in
real-mode operation.

MORE INFORMATION
================

To prevent a memory check on IBM and many compatibles (warm boot), you should
store the value 0 x 1234 in the memory location at 0040:0072. On 100-percent IBM
BIOS compatible machines, an alternative method is to call int 19h instead of
jumping to the address mentioned above.

Sample Code
-----------

  ; Assemble options needed: none

  .MODEL small

  .CODE

  Start:
      mov ax, @data                 ; Load ds with data segment
      mov ds, ax

      mov ax, 40h                   ; These three lines cause a memory
      mov es, ax                    ; test NOT to be performed. To
      mov WORD PTR es:[72h], 1234h  ; do a memory test, remove them.

      jmp DWORD PTR b_vec           ; Jump to the reboot address

  .DATA
  b_vec   DW 00000h                 ; Offset of reboot vector
          DW 0FFFFh                 ; Segment of reboot vector

  .STACK

  END Start

Additional query words: 5.10 5.10a 6.00 6.00a 6.00b

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Keywords          :  
Technology        : kbMASMsearch kbAudDeveloper kbMASM510 kbMASM600 kbMASM500 kbMASM600a kbMASM510a kbMASM600b
Version           : :5.0,5.1,5.1a,6.0,6.0a,6.0b

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