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Date:      Thu,  2 Aug 2001 21:14:18 +0200 (MET DST)
From:      thenamelessone@abacho.de
To:        freebsd-hackers@FreeBSD.org
Subject:   Re: How to visit physical memory above 4G?
Message-ID:  <-1092334714.996778934042.JavaMail.root@aaron.unimessage.net>
In-Reply-To: <Pine.BSF.4.21.0108021353000.41008-100000@InterJet.elischer.org>

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why is nobody trying to read the intel documentation???
1.page adress extension is available since pentium pro.
2.you can only adress the 36 bit adress space when 
  paging is enable
3.a flag has to be set
4.the linear adresses are a bit different

without PAX:
bits 31 thru 22 are an offset into the page directory
bit 21 thru 12 are an offset into the page table
bit 11 thru 0 are an offset into the page

with PAX:
bits 31 thru 30 are an offset into the page directory pointer table
bits 29 thru 21 are an offset into the page directory
bits 20 thru 12 are an offset into the page table
bits 11 thru 0 are an offset into the page

sometimes its very useful if you did some low-level (REAL low-level)
coding

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