From mboxrd@z Thu Jan  1 00:00:00 1970
From: ron minnich <rminnich@lanl.gov>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] pathetic
In-Reply-To: <20040225154145.G7383@edinburgh.cisco.com>
Message-ID: <Pine.LNX.4.44.0402250900080.9147-100000@maxroach.lanl.gov>
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Date: Wed, 25 Feb 2004 09:02:45 -0700
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On Wed, 25 Feb 2004, Derek Fawcus wrote:

> As I understand it,  this NX bit is at the page level,  and so can alter
> a individual 4K page within the linear memory space.  If they used the
> segment facility to do this,  the memory space would be non linear and
> on the x86 this'd take a massive performance hit (48 bit addresses).

well ... on e.g. linux, the segment descriptors are used. Paging on x86 is
in addition to segments. segment are earlier in address translation path
than pages, and they are still there when paging is turned on. It's quite
weird.

I don't see an NX bit in my pentium manual.

ron