Re: Big Real Mode above 4Gb

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Article #199

#199

From: Herman Dullink
Date: Sun, 08 Sep 2002 10:56

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Hi,

>I understand the basic principles of Big Real Mode where the selector limit
>is set to 4Gb.  Is there a way to have the base be at 4Gb and the limit at
>8Gb?
No, the limit register is a 20 bit register, with a 1 byte or 4KB
granularity.
There for 4GB max. Which _is_ the maximum of the linear address space
of a 80386 and compatible CPU.

The only way to address more than 4GB (if your system _has_ more than 4GB)
is to use paging.
The problem is, that only 80386 and some 80486 CPUs can have paging
enabled in real mode, and have a physical address space of 4GB.
The CPU's which _do_ have a larger physical address space cannot have
paging enabled in real mode...

H

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From: "Herman Dullink" <dullink@hetnet.nl>
Newsgroups: comp.lang.asm.x86,intel.microprocessors.pentium_iii
Subject: Re: Big Real Mode above 4Gb
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