Message-Id: <200406030303.i5333nof009223@orion.dwf.com>
To: Brian Gerst <bgerst@didntduck.org>
cc: root@chaos.analogic.com, reg@dwf.com, linux-kernel@vger.kernel.org,
       reg@orion.dwf.com, linux@horizon.com, reg@orion.dwf.com
From: clemens@dwf.com
Subject: Re: Intel 875 Motherboard cant use 4GB of Memory. 
In-Reply-To: Message from Brian Gerst <bgerst@didntduck.org> 
   of "Wed, 02 Jun 2004 21:11:25 EDT." <40BE7ABD.1050609@quark.didntduck.org> 
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Date: Wed, 02 Jun 2004 21:03:49 -0600
Sender: linux-kernel-owner@vger.kernel.org
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Wrong.  Ever since the Pentium Pro, x86 processors have had 36-bit 
*physical* addressing.  This is why PAE-mode paging was introduced.  A 
sane BIOS would configure the memory controller to remap some of the 
memory above 4G physical to allow for memory mapped devices.  It sounds 
like this board's BIOS isn't doing that, or at least not reporting it in 
the e820 map.

---

Hummm.

Let me restate the fact that I dont understand how PC hardware works, but
I can understand how the area for PCI devices has to come out of the
KERNEL address space, but why does it have to be subtracted from the USER
address space too?


-- 
                                        Reg.Clemens
                                        reg@dwf.com


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