Re: reboot with qb

 BBS: Inland Empire Archive
Date: 04-17-92 (20:48)             Number: 90
From: STEVE HALKO                  Refer#: NONE
  To: DICK DENNISON                 Recvd: NO  
Subj: Re: reboot with qb             Conf: (2) Quik_Bas
DD> JV> OUT &H64, &HFE
DD> JV> ^^^^^^^^^^^^^^
DD> JV>    |   It performs a cold boot via the keyboard reset line.
DD>MB>         |
DD>MB>         |
DD>MB>  What would this be if you wanted a 'warm' boot?

DD>You cannot use this method for a warm boot - for that you'll need the
DD>far jmp with call absolute.  Also, this method should not work on a
DD>8088 or 8086 for a very interesting reason having to do with protected
DD>mode reentrance.  (Steve Halko - can you elaborate on this ??)

  Er . . . you must have mistaken me for an expert!  I think it won't
  work on 8088/8086 machines because I don't believe they even have a
  port 64h.  Port 64h was added in IBM AT's as a means of accessing the
  newly added 8042 Keyboard Controller.  XT's used an 8048 Keyboard
  Controller which was not directly accessible to the programmer -
  however, some keyboard parameters and functions were available thru
  ports 60h/61h (which were connected to the 8255 Programmable
  Peripheral Interface, PPI).

  On a 286, the usual use of the OUT &H64, &HFE is to go from protected
  mode to real mode.  In 386/486's, there's a much more elegant (and
  faster) way, but the OUT will still work, I believe.

 * SLMR 2.1a * It's my parity and I'll baud if I want to!

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