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Path: utzoo!dciem!nrcaer!cognos!brianc
From: brianc@cognos.UUCP (Brian Campbell)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Code to perform warm reboot.
Message-ID: <389@cognos.UUCP>
Date: Mon, 23-Feb-87 13:32:51 EST
Article-I.D.: cognos.389
Posted: Mon Feb 23 13:32:51 1987
Date-Received: Wed, 25-Feb-87 03:38:14 EST
References: <424@omepd>
Distribution: world
Organization: Cognos Inc., Ottawa, Canada
Lines: 27

in article <424@omepd>, perry@omepd.UUCP says:
> 
> In article <3258@j.cc.purdue.edu> tim@j.cc.purdue.edu (Timothy Lange) writes:
>>The following is Macro code to make an IBM PC and true compatibles
>>perform a warm reboot.
>> [...showing a simple assembler program to jump to F000:FFF0...]
> 
> By this diction, what you propose (a jump to address F000:FFF0) is a
> COLD BOOT. F000:FFF0 is the place where the processor begins to execute
> when it is reset (i.e., when the power is turned on). The first thing it
> does up there is to run test loops and initiate the memory check. Please
> wait...
> 
> There is a simple way to perform a real `warm' boot on an IBM PC. Just do
> an `INT 19H' instruction. This will reload MSDOS and restart the configuration
> process (reading CONFIG.SYS, executing AUTOEXEC.BAT etc.) without first doing
> the hardware checks. Believe me, it's faster.
> 
> The only advantage of a Cold Boot is that you're jumping into ROM, so no-one
> can intercept you. Programs can intercept interrupt 19H and delay or prevent
> the boot (which may be a good thing for sensitive programs that have to do
> cleanup operations). A `JMP F000:FFF0' kills the machine immediately.

  Small correction: a JMP F000:FFF0 is only a COLD boot if you have done
no WARM boots since power-on.  There is a useful little flag word at
some offset in the BIOS data area.  If it is set to 1234h the CPU,
memory and other tests will not be performed.