muta...@gmail.com  wrote:   
   > On Monday, October 10, 2022 at 6:18:47 PM UTC+8, Joe Monk wrote:   
   > > > Not sure what you're talking about.   
   > > >   
   > > > This is a once-off instruction to be executed.   
   > > >   
   > > Says who? What will stop me from executing it any time I want?   
   >   
   > Nothing will stop you, but I doubt it will do   
   > anything useful when the os has loaded all it's   
   > content with a particular shift   
   > value in effect and you choose   
   > to switch it.   
      
   Hmm, you said you do not want mode bits (to switch between   
   real/protected, etc).  But now you what you propose is   
   mode bit.  So, do you like mode bits or no?   
      
   > An 80386 should support a shift of 16.   
   > Almost no extra circuitry would be required.   
      
   386 could address full 32-bit address space, except that extra   
   circuitry masked high bits of offsest.  In other words, 386   
   could have what is known as "unreal mode" as real mode.   
   Intel did not do that, and at least part of this was politics:   
   they did _not_ want 32-bit capable real mode.  Instead   
   they wanted people to switch to protected mode.   
      
   Coming back to modes: main problem with modes is that various   
   applications "live in different words", you can not simply   
   call function in binary library compiled for different mode,   
   you need to recompile or have some wrapper code handling   
   mode switching.  There is some code in OS to support modes.   
   This leads to pragmatic approach: one uses modes to have   
   smooth transition.  But after transition old mode should be   
   killed.  And that is happening: OS-es for new PC processors   
   work in protected mode, boot process is in protected mode.   
   And real mode programs, if you want to run them work via   
   emulation.  Basically world is ready to remove real mode   
   from processors.  OK, there is a glitch, there is still   
   "system management mode" that is more or less real mode,   
   but only available to BIOS.  But "real" real mode and VM86   
   could be removed.   
      
   You say that Intel should keep real mode alive, but most   
   people think that we are in better world now.  That was   
   long transition.  And efforts to keep real mode alive probably   
   would make it slower and more painful.   
      
   If I was in business of correcting history, I would probably   
   add "VM86" mode to 286.  Of course, big point of VM86 is   
   ability to use paging.  But even limited mode allowing to   
   run 8086 programs in first 1M of memory while keeping   
   everything under control of protected mode OS could   
   speed up transition to protected mode.   
      
   --   
                                 Waldek Hebisch   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)