From: noemail@basdxcqvbe.com   
      
   On Mon, 5 Jul 2021 06:45:43 -0700 (PDT)   
   "muta...@gmail.com"  wrote:   
      
   > On Monday, July 5, 2021 at 7:24:11 PM UTC+10, Rod Pemberton wrote:   
   >   
      
   > > In other words, other than E820h or perhaps VESA, I   
   > > don't understand why you need the BIOS for that much,   
   > > or why I'm getting the strong impression PDOS is really   
   > > dependent upon the BIOS, especially for file I/O.   
   >   
   > It's extremely dependent.   
   >   
   > And now that I know that the BIOS even provides an   
   > INT 14H, I'm a very happy camper, because my eyes   
   > light up and I see "SeaBIOS and bluetooth!".   
      
   By Int 14h, you mean BIOS serial I/O?  Just checking   
   because RBIL has lots of other stuff listed ...   
      
   > And I had another look at code you provided me too.   
   > I never really liked the look of this bit:   
   >   
   > https://sourceforge.net/p/pdos/gitcode/ci/master/tree/src/lldos.asm   
   >   
   > mov ax, 02401h   
   > int 015h   
   >   
   > And I commented it out. But just in the last few days I   
   > realized that this was the only place I actually manipulate   
   > the hardware. I looked up the interrupt number you   
   > provided. And it looks to me like if I use that interrupt,   
   > I will be decoupled from all hardware other than the   
   > CPU. Which sounds like a great place to be. In the same   
   > way that the people who wrote the INT 14H spec had   
   > never even heard of bluetooth.   
   >   
      
   ...   
      
   > I looked up the interrupt number you provided.   
      
   Which interrupt was that?   
      
   I think I mentioned three Int 15h's recently:   
   AH=87h (copy extended memory)   
   AH=89h (switch to PM)   
   AX=E820h (extended memory map)   
      
   > And I commented it out. But just in the last few days I   
   > realized that this was the only place I actually manipulate   
   > the hardware.   
      
   Are you saying you intend to enable the A20   
   line via the BIOS Int 15h, AX=2401h call, so   
   as to make PDOS hardware independent? ...   
      
   I.e., it seems like you're saying you're   
   eliminating enabling A20 via port programming.   
      
   If so, then   
   a) that's a very bad idea, and   
   b) I didn't give you that int.   
      
   James and I found serious problems with the   
   BIOS A20 functions we tested, which mostly   
   failed for 10 motherboards.  The keyboard   
   and PS/2 port enable methods work, except   
   one motherboard which pre-dated PS/2.   
      
   "Machine Characteristics - A20 Controls"   
   http://aodfaq.wikidot.com/mc-a20-controls   
      
   "Machine Characteristics"   
   http://aodfaq.wikidot.com/machine-characteristics   
      
   --   
   What is hidden in the ground, when found, is hidden there again?   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)