Path: utzoo!attcan!telly!nebulus!druid!darcy
From: darcy@druid.uucp (D'Arcy J.M. Cain)
Newsgroups: comp.sys.ibm.pc
Subject: Re: System boot and INT 19
Keywords: system boot
Message-ID: <1990Jan10.221751.2656@druid.uucp>
Date: 10 Jan 90 22:17:51 GMT
References: <945@excelan.COM> <77@qmsseq.imagen.com> <357@clover.warwick.ac.uk>
Reply-To: darcy@druid.UUCP (D'Arcy J.M. Cain)
Organization: D'Arcy Cain Consulting, West Hill, Ontario
Lines: 40

In article <357@clover.warwick.ac.uk> bsrdp@warwick.ac.uk (Hylton Boothroyd) writes:
>In article <77@qmsseq.imagen.com> pipkins@qmsseq.UUCP (Jeff Pipkins) writes:
>> The int 19h vector is supposed to do a warm boot.
>
>I wonder how many of those who repeat these recipes have tried them.
>The use of INT 19 is curiously under-documented even in the MSDOS
>interrupt list.
>
>In my current version of MSDOS (3.20), the MSDOS external command
>PRINT.EXE is in fact a TSR which hooks INT 19 for its own purposes.  I
>haven't traced through the use of INT 19, or traced whether it hands on
>gracefully up the chain, but I do know that the warm-start recipes that
>appear here every so often simply don't work for me.
>
>It remains a mystery how to replicate the warm start effect of
>Ctrl-Alt-Del.  [And I have worked through several of the likely things
>in SIMTEL.]
First let me add some information.  The following will do a warm boot:

	mov	ax, 40h
	mov	ds, ax
	mov word ptr [72h], 1234h
	jmp	0ffff:0000

Note the value to stuff into location 0472h is 1234 HEX.  The ROM BIOS
looks at that location to decide whether it was just turned on or if it
is booting from a live system.

Second can anyone tell me if int 19h will restore interupt vectors
properly if they were changed using DOS int 21h service 25h (Set
Interupt Vector) or does the program have to catch this as well?  I
always assumed the former but some of the discussion here suggests
the latter.


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D'Arcy J.M. Cain (darcy@druid)     |   Thank goodness we don't get all 
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