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To: Bruce Evans <bde@zeta.org.au>
cc: CVS-commiters@freefall.cdrom.com, cvs-sys@freefall.cdrom.com
Subject: Re: cvs commit: src/sys/i386/i386 locore.s 
In-reply-to: Your message of "Sun, 16 Apr 95 22:10:52 +1000."
             <199504161210.WAA05197@godzilla.zeta.org.au> 
From: David Greenman <davidg@Root.COM>
Reply-To: davidg@Root.COM
Date: Sun, 16 Apr 1995 05:20:39 -0700
Sender: commit-owner@FreeBSD.org
Precedence: bulk

>>  Modified:    sys/i386/i386 locore.s
>>  Log:
>>  Remove gratuitous waste of 2K of memory for BIOS variables. We never load
>>  the kernel at 0-640k; we haven't had the ability to do that since before
>>  2.0R. Furthermore, I fail to see how putting an instruction at 0 and then
>>  doing a .org 0x500 is going to prevent the stuff from getting clobbered
>>  in the first place; a.out is just too stupid to know about sparse address
>>  spaces.
>
>boot.c has `#ifdef REDUNDANT' code to skip over the "BIOS variables" between
>(startaddr + 0x400) and (startaddr + 0x4ff) even when startaddr != 0.
>Removing the padding is a bit dangerous because bootstraps older than approx.
>1995/01/25 don't have `#ifdef REDUNDANT' so they depend on the padding.

   This would skip over the movw instruction at the beginning (which wouldn't
set the warmstart). With the new boot structure, numerous changes to the
startup flags, etc, we more or less require people to update the bootblocks
anyway. I don't think this is a problem.

-DG