Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!willett!ForthNet
From: ForthNet@willett.UUCP (ForthNet articles from GEnie)
Newsgroups: comp.lang.forth
Subject: Forth on the Intel 80386
Message-ID: <624.UUL1.3#5129@willett.UUCP>
Date: 7 Mar 90 02:24:27 GMT
Organization: Latest link in the ForthNet chain.  (Pgh, PA)
Lines: 52


 Date: 03-05-90 (09:14)              Number: 1775 (Echo)
   To: MIKE SPERL                    Refer#: 1772
 From: PETE KOZIAR                     Read: NO
 Subj: PROTECTED MODE 386            Status: PUBLIC MESSAGE

 Well, I'm going to have to think a little more on this, but here's some 
 stuff off the top of my head about the linear address mode of the 386: 

 1. The 386 memory management is designed around a minicomputer model, 
 using the idea of "priviliges."  There is an "operating system" that 
 can do some special things (like change memory maps), and an 
 "application program" that is restricted.  If there is already an 
 operating system loaded (like DESQview or Windows), it takes the role 
 of the operating system, so a lot of the operating-system-like 
 functions are not allowed, or will be allowed only through special 
 operating-system calls when real 80386 Opsys's finally arrive 
 (Windows/386 really isn't a 32-bit opsys, OS/2 386 isn't out yet, 
 and DESQview forces the 386 into the "multiple-8086" mode). 

 2. DOS and the BIOS assume 8086 emulation mode, so every time you want 
 to call DOS or BIOS, you must return the machine to its "boot-up" 
 configuration.  This can cause real headaches if the data you want to 
 send to the opsys is in a piece of memory that disappears when you 
 restore to the 8086 map.  You could probably double-buffer the data, 
 but it wouldn't be pretty. 

 3. There are apparently "DOS-extenders" around that give you the linear 
 address space.  I have never used one, and have no idea how they work. 

     I haven't crossed this bridge just yet.  I have an application 
 where it would really be nice to be able to use some of the features of 
 a real opsys (like shared regions), but I can get around it for now. 

     By the way, the Laxon/Perry F83 was a lot more readable than F-PC. 
 L&P had some comments in the shadow screens; it doesn't look like any 
 of the shadow-comments made their way across into F-PC. 

     I think the first step on the way to a real 386 FORTH would be to 
 use the instructions that are available even in the 8086 emulation 
 mode.  It would certainly speed up double-precision, and the extra 
 segmentation registers might make some things (like @L) a bit easier. 

      Here's today's trivial speed-up.  Three of the most-used constants 
 are certainly -1, 0 and 1.  F83 defined them as CODE words, but F-PC 
 does not.  Their definitions are easy, and left as an exercise to the 
 reader. 
 ---
  * Via Qwikmail 2.01  The Baltimore Sun 
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