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From: zech@leadsv.UUCP (Bill Zech)
Newsgroups: comp.sys.ibm.pc
Subject: Re: System boot
Summary: I was partially wrong...
Message-ID: <9388@leadsv.UUCP>
Date: 13 Jan 90 04:01:41 GMT
References: <25ab3ab5@ralf>
Organization: LOCKHEED, Sunnyvale, CA
Lines: 31

In article <25ab3ab5@ralf>, Ralf.Brown@B.GP.CS.CMU.EDU writes:
> In article <9312@leadsv.UUCP>, zech@leadsv.UUCP (Bill Zech) wrote:
> }INT 19
> }        This is a DOS boot ONLY.  The BIOS interrupts are *NOT*
> }        reset.  Note that INT 19 is a DOS interrupt, not a BIOS int.
> 
> It is *not* a DOS interrupt.  INT 19h is a BIOS interrupt, 
> but points right at
> the code with loads and then executes the boot sector.	
> DOS does not know or
> care about INT 19h (except insofar as VDISK.SYS uses a stub INT 19 handler to
> locate the data from previous invocations).
> 

Yes, my memory failed me partly, but DOS DOES care about int 19H.
DOS intercepts it and has lots of code which it performs to reset
various interrupts it was using, then reprograms the int 19H vector,
and fires int 19H to reboot.  

Dump out location 0:64 and you will see it points to code at 70:xxxx
inside DOS.  

BTW, the BIOS cold and warm start code fires int 19H internally
to boot the system.

All in all, jumping to the machine's restart location is best.

P.S.  I've never seen your interrupt list.  Does it have anything
      new in it, not covered by the various books out there now?
      Most of the secrets of yesteryear are now pretty common.

- Bill