Path: utzoo!attcan!uunet!mcsun!ukc!warwick!bsrdp
From: bsrdp@warwick.ac.uk (Hylton Boothroyd)
Newsgroups: comp.sys.ibm.pc
Subject: Re: System boot and INT 19
Keywords: system boot
Message-ID: <361@clover.warwick.ac.uk>
Date: 12 Jan 90 17:43:11 GMT
Organization: Warwick Business School
Lines: 30

In article <357@clover.warwick.ac.uk> bsrdp@warwick.ac.uk I wrote:
> > The int 19h vector is supposed to do a warm boot.
> ...
> 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.

Thanks to those who posted directly to me or here in this newsgroup I
now know:
  a) INT 19 is not the correct general route, and I cannot expect it to
     work,
  b) setting 0040:0072 to 1234hex and jumping to ffff:0000 is the
     standard IBM PC way to achieve a warm boot, and I can reasonably
     expect it to work,
  c) (b) will work only if the BIOS ROM created by a manufacturer for
     his particular machine emulates this particular feature of the IBM
     PC - it is nothing to do with how MSDOS works,
  d) the manufacturer of my XT clone arranged to test for 1234 in his
     BIOS ROM but by mistake included code that alters 0040:0072 before
     the test is reached!
  e) as a result of (d) my XT clone has no proper warm boot from
     Ctrl-Alt-Del - it just gives a cold boot.

I feel very foolish about (e). Evidently I have become so used to what
I am working with that I have long ago ceased to notice this flaw. But
this thread has at least made me explore it properly.

Hylton