ID Number: Q68805
5.10
MS-DOS
Summary:
You can perform a complete reboot (cold boot) on an 8086-based machine
by jumping to the address F000:FFF0. 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.
Code Example
------------
.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 0FFF0h ; Offset of reboot vector
DW 0F000h ; Segment of reboot vector
.STACK
END Start