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From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Help w/copy protection?
Message-ID: <723@neoucom.UUCP>
Date: Thu, 8-Oct-87 23:02:18 EDT
Article-I.D.: neoucom.723
Posted: Thu Oct  8 23:02:18 1987
Date-Received: Mon, 12-Oct-87 01:13:13 EDT
References: <379b48f5.448d@apollo.uucp> <620008@hpclisp.HP.COM>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 35
Summary: Warmboot magic cookie


The normal procedure to reboot PeeCees and compatibles is to enter
the ROM BIOS.  You can do this by performing a long jump thusly:

	JMP F000:FFF0

This, more than likely, will perform a cold boot.  To get a warm
boot, you can feed a magic cookie into low memory.  If the magic
cookie is present, the ROM BIOS will skip over the memory check and
video mode reset stuff.  Note that DOS INT 19H (I think that is the
number) purports to perform a warm boot, but this seems broken on a
lot of klone musheenz.  The magic cookie always works.  Perform it
thusly:

	MOV AX,0040	;set up segment offset
	MOV DS,AX	;set segment reg.
	MOV AX,1234	;neat cookie, huh?
	MOV [0072],AX	;cookie 1234 --> (0040:0072)
	JMP F000:FFF0	;jump to BIOS

you can easily enter the above sequence using DEBUG.COM.  Refer to
your manual [programmer's axiom:  RTFM] for details on using debug.
I have found being able to do a warmboot to reset a machine running
procomm via the above from remote to be very useful.

Hope this helps!

Bill


Bill Mayhew   Electrical Engineering
Division of Basic Medical Sciences
Northeastern Ohio Universities' College of Medicine
Rootstown (what a name!), OH  44272-9989  USA    phone:  216-325-2511
wtm@neoucom.UUCP  (...!cbosgd!neoucom!wtm)