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Date: Wed, 23 Feb 2005 11:47:34 +0100
From: Gisle Vanem <giva AT bgnett DOT no>
Subject: Re: Differences in LPT1 base address in protected/real mode?
To: djgpp AT delorie DOT com
Message-id: <0b4a01c51995$14f74ca0$0600000a@broadpark.no>
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Reply-To: djgpp AT delorie DOT com

"Karl-Heinz Pischke" wrote:

> if I try to get the LPT1 base address at 0x408 with inportw I get
> FFFFh back instead of the expected 7803h ... as I googled around just
> now I found out that there is a significant difference in the
> addressing of memory between real and protected mode ... I guess this
> is the crux of the 'phenomenon' ... unfortunately I didn't found any
> document so far that could help me with finding the correct address of
> 0040h:0008h in the protected mode ... is anyone here in the know how
> to get the LPT1 base adress from bios in protected mode?

DOS memory (range 0-1MB physical) must be refered to using the _dos_ds 
selector. For example:

#include <sys/farptr.h>
#include <go32.h>
unsigned short base = _farpeekw (_dos_ds, 0x408);

--gv