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Date:      Tue, 17 Dec 2002 16:09:59 -0500 (EST)
From:      John Baldwin <jhb@FreeBSD.org>
To:        Peter Jeremy <peter.jeremy@alcatel.com.au>
Cc:        cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG, "M. Warner Losh" <imp@bsdimp.com>
Subject:   Re: cvs commit: src/sys/boot/i386/boot2 boot2.c
Message-ID:  <XFMail.20021217160959.jhb@FreeBSD.org>
In-Reply-To: <20021217202351.GO15322@gsmx07.alcatel.com.au>

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On 17-Dec-2002 Peter Jeremy wrote:
> On 2002-Dec-17 12:40:38 -0500, John Baldwin <jhb@FreeBSD.ORG> wrote:
>>We could shave a lot of room off of boot2 by having it be a real-mode
>>application instead of a protected mode one.  This would allow us to
>>ditch all of BTX.  However, we would either need to use a C compiler
>>that can generate real-mode code (gcc can't AFAIK) or we need to
>>write it all in assembly.  I'd really like to avoid the latter if at
>>all possible.  Any chance that gcc might could be tweaked to add a
>>real-mode target?
> 
> 80x86 real mode (16-bit) is significantly different to 32-bit mode -
> the addressing modes are almost completely different for starters.
> Supporting real-mode and generating decent compact code in particular
> is going to require significantly more than a simple 'tweak' to gcc.

I'm aware of that.  However, I was wondering if there already existed
a real-mode backend that could be enabled in our system compiler by a
simple configuration tweak. :)

-- 

John Baldwin <jhb@FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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