From:	mharris AT blackwidow DOT saultc DOT on DOT ca
Date:	Tue, 4 Feb 1997 23:06:18 -0500 (EST)
Reply-To:	mharris AT blackwidow DOT saultc DOT on DOT ca
To:	David Cantrell <david AT diablo DOT eimages DOT co DOT uk>
cc:	opendos AT mail DOT tacoma DOT net
Subject:	Re: [opendos] speeding up command.com
In-Reply-To:	<1357142637-14672907@diablo.eimages.co.uk>
Message-ID:	<Pine.LNX.3.95.970204230229.166z-100000@capslock.com>
Organization:	Total disorganization.
MIME-Version:	1.0
Sender:	owner-opendos AT mail DOT tacoma DOT net

On Mon, 3 Feb 1997, David Cantrell wrote:

> > > OpenDOS is for x86 processors, right?
> > > You're not going to break things by inserting a little ASM code - >
> >
> >   Maybe we can use some 386, 486, 586 or MMX specyfic opcodes inside
> > Open DOS. Executables will be smaller and faster but all machines
> > with less than (386...MMX) could be dropped into trash.
> 
> There would be no benefit in using 386 (or higher) instructions.  All 
> existing DOS apps expect to use a 16-bit operating system, so even if 
> the app is 32-bit internally (such as those compiled with DJGPP), it 
> still has to go 16-bit for talking to device drivers - such as sound 
> cards, CDs, hard disks, and for allocating memory.  If you rewrote 
> these as 32-bit code, you would still have to provide 16-bit 
> emulations of them, just like Win95 does.  And you would get the same 
> code-bloat and horrendous number of bugs as Win95.

Although the OS would still be 16 bit, it doesn't mean that it
couldn't use the 386+'s extended 32 bit registers, segment regs
and new instructions.  Granted they wouldn't double performance
but there may be useful speedups.  First we need to see the code
and see where things are slow.  (ANSI386.SYS?)  :o)

> Anyway, the performance advantage would not be noticeable.  You spend 
> very little productive time at the command prompt, so to gain a 
> performance increase from going 32-bit, you would either have to 
> rewrite all your APPS to be 32-bit, or be the demon-batch-coder-
> from-hell and do all your work in COMMAND.COM.

The command prompt is command.com, using 386 instructions/regs
could possible speed up some things but probably not too
perceiveably, however INSIDE the kernel is a different story.

Mike A. Harris        |             http://blackwidow.saultc.on.ca/~mharris
Computer Consultant   |    My webpage has moved and my address has changed.
My dynamic address: http://blackwidow.saultc.on.ca/~mharris/ip-address.html
mailto:mharris AT blackwidow DOT saultc DOT on DOT ca

    Caldera sues Microsoft - Visit Caldera's website: www.caldera.com

- Raw text -