Date: 17 May 1997 13:03:50 -0000
Message-ID: <19970517130350.16074.qmail@dns01.ops.usa.net>
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To: opendos AT delorie DOT com
From: b52g AT usa DOT net (JP Morris)
Subject: Re: 32 bit dos
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>
>Now as most people have known, Dos makes extensive use of software
>interrupts to do practically everything.  The OS is so heavily ISR
>driven [with many duplicate features which return different values]
>that it is a real pain to get 16 bit applications working in a
>flat 32bit address space. [such as a 32 bit virtual paged memory model]
>
>The main reasons for a 32 bit dos are:
>
>	1.) faster memory transfers.
>	2.) more memory available to programs.

Please remember that 32 bit and 'more memory' are NOT synonymous, until last
month I was quite happy to use DPMI/16, which gave me all the memory I could
eat,
as well as the familiar seg:offset memory model.  
I habitually designed my data structures around the 64k limit, easy really.

Even my assembler code worked after a simple recompilation.
In addition, it also works on 286 processors, albeit with a limit of 16mb
on those systems.  But then DOS/4GW has a 16mb limit AFAIK.

>Ofcourse if you have to prefrom conversions translating the old seg:off
>to a flat 32, you incure a lot of overhead.  Ofcourse native programs

>would take full advantage, however, you'd have overhead in that you would
>still have thunk code.

Grooh yes.. my 32-bit compiler doesn't have interrupt handling facilities!
I have to use some wierd code that Ethan Brodsky lent me.  Generates a thunk
that calls
'nowhereland', an empty 48-bit pointer that is filled in later to point to
the int handler.

The only reason I changed was to use SVGA, I couldn't find a quick way to do
this in 
16-bit code.  The 32-bit program is slower and less stable.
It also dies under NT and win95 dos boxes, but that's 'cause of the wierd
32RTM extender.

So the moral is to remember that the 286 has a protected mode as well.

>
>	Now this sounds like the ultimate in brian dead ideas,
>	but what if someone were to build a lite 32 bit dos..
>	with a 16 bit DOS BOX?

It wouldn't work with Real Flat programs, Ultima 7, and my demo collection.
When we get a 32-bit DOS, we'll also need an emergency backdoor into REAL-MODE,
so that V86-allergic programs can be run.

>Sort of like the Rhapsody needs a MacOS box.. [never mind Rhapsody is

What's Rhapsody?  I thought it was a composition package on the Arc way back..
obviously there is another one.

>also comming out for the Pentium chip in a native format, and that
>it's programs will also run under Windows95 & NT under a Rhapsody box
>but that is niether here nor there]
>
>
** b52g AT usa DOT net ** http://members.tripod.com/~JPMorris **
Data control & IBM, Science is mankind's brother
but all I see is draining me & my Plastic Fantasic lover!
 -- Jefferson Airplane