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From: brown@nicmad.UUCP (Vidiot)
Newsgroups: comp.sys.ibm.pc,comp.sources.wanted
Subject: Re: Is it possible to re-boot a PC from a program ?
Keywords: reboot.exe
Message-ID: <3786@nicmad.UUCP>
Date: 20 Mar 89 15:13:27 GMT
References: <830@psueea.UUCP> <265@humming.UUCP>
Reply-To: brown@nicmad.UUCP (Vidiot)
Distribution: na
Organization: Vidiot's Hangout
Lines: 87

In article <265@humming.UUCP> simcha@humming.UUCP (Simcha Lerner) writes:
<In article <830@psueea.UUCP> alexc@psu-cs.cs.pdx.edu (Alex Chan) writes:
<>
<>Hi there,
<>
<>	Is it possible to write a program to reboot a PC ?
<>	( I mean a " cold boot " with memory check. ) and how
<>	could I do it ?
<>
<
<This is quite easy.  A cold boot is initiated by jumping to address
<FFFF:0000 in real mode - this being the address that the processor
<goes to in the event of a reset.
<
<If you wish a warm boot, load 1234 into 40:72 (all of these numbers are
<hex).  This will cause the POST (Power On Self Test) to be skipped.
<
<Given the tiny size of this program, you can easily create it via debug.

Yep, it is very easy.  Attached is an assembly listing that you run through
MASM to create a stand-alone program and an object file that can be linked
in with other programs (which I have done).


                page    60,132
                title   REBOOT.ASM = Performs a Warm System Boot =

                PUBLIC REBOOT

;=======================================================================;
;                                                                       ;
;       This segment is used to reference a "JMP" instruction in        ;
;       ROM which branch to the reboot code in ROM.                     ;
;                                                                       ;
;=======================================================================;

rom_seg         segment at 0ffffH
boot_jmp        label   far
rom_seg         ends

;=======================================================================;
;                                                                       ;
;       This segment is used to reference a word in the BIOS data       ;
;       area which is used to determine if a WARM or COLD reboot        ;
;       should be performed by the reboot code in ROM.                  ;
;                                                                       ;
;=======================================================================;

bios_seg        segment at 0040H
                org     bios_seg+72H
boot_flags      label   word
bios_seg        ends

cold_boot       equ     0000H           ;Value to indicate COLD reboot
warm_boot       equ     1234H           ;Value to indicate WARM reboot


                page
;=======================================================================;
;                                                                       ;
;       The following lines set the boot flags in the BIOS Data         ;
;       Area and then invoke the boot code in the BIOS ROM.             ;
;                                                                       ;
;=======================================================================;

code_seg        segment
                assume  CS:code_seg, DS:code_seg
                org     code_seg+100H

reboot          proc
                mov     AX,bios_seg
                mov     DS,AX           ;Point to BIOS Data Area
                assume  DS:bios_seg
                mov     boot_flags,warm_boot

                assume  DS:rom_seg
                jmp     boot_jmp        ;Jump to Reboot Code
reboot          endp

code_seg        ends

                end
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