Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!hsdndev!wuarchive!psuvax1!psuvm!frecp12!zeches
From: ZECHES@FRECP12.BITNET (Nicolas Zeches)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: BIOS ROM?
Message-ID: <91060.221902ZECHES@FRECP12.BITNET>
Date: 2 Mar 91 02:19:01 GMT
References: <177@beep.UUCP>
Distribution: usa
Lines: 25
Organisation: ECP-Paris France

In article <177@beep.UUCP>, kris@beep.UUCP (Huh?) says:
>     Does anyone out there know anything about hacking BIOS ROMs?  When
>I try using the "jmp 0x0ff0000" (or whatever) to do a "warm" hardware
>restart, it doesn't work.  The system just seems to hang.
>
>     I suspect the problem may be in my BIOS ROM.

Well, i wonder if it really comes from you BIOS... First of all, the warm
boot BIOS address is FFFF:0000. A simple jump to this address usually works.
However, i've already had a problem withg a PS/2 that didn't accept to reboot
How come ? The bios segment (40h) contains some variable that is useful for a
warm boot : the word at address 40:72 (hex) should contain the value 1234h
Here is an example of warm boot routine :
   MOV AX,0040h
   MOV DS,AX
   MOV AX,1234h
   MOV [0072h],AX
   JMP FFFF:0000

That's all folks ! I hope it will work for you...

                                Virtually.

                                          Nicolas Zeches
                                       ZECHES@FRECP12.BITNET