From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stas Sergeev <stssppnn@yahoo.com>
Subject: Re: A20 Address line - XMS issue
Date: Sat, 07 Dec 2002 01:29:41 +0300
Sender: linux-msdos-owner@vger.kernel.org
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Hello.

Bart Oldeman wrote:
> HIMEM.SYS might be able to
> run in DOSEMU if DOSEMU would implement int 0x15/0x87 to copy extended
> memory though.
It can't.

> HIMEM.SYS might be able to
> run in DOSEMU if DOSEMU would implement int 0x15/0x87 to copy extended
> memory though.
Real mode is an ultimate requirement
for himem to work. You can't set up
the Big Real Mode from within v86.
Here is the source:
http://honors.tntech.edu/~will/fileformat.virtualave.net/programming/himem/xm386.asm
Here is the relevant part:
---
mov     bx, descRealBig - OurGDT ; Special 4Gb selector
lgdt    qword ptr cs:[GDTPtr]

mov     eax, cr0
or      al,1
mov     cr0, eax         ; Go into Protected Mode
                          ; NOTE: NMIs will kill us!!!
---
Both "lgdt" and "mov cr0" are priviledged.