Dailydave: Re: luckily, there are no dumb questions

[Andrew Cushman <andrewcu () windows microsoft com>]

Not all chips have four rings.  Mips and alpha and i think ppc all had
user and supervisor modes.  x86 has four rings, and NT used three of
them for a while, but.... x64 has only user/supervisor when running in
64 bit mode.

 

 

 

From: dailydave-bounces () lists immunitysec com
[mailto:dailydave-bounces () lists immunitysec com] On Behalf Of Andreas
Junestam
Sent: Thursday, June 07, 2007 1:36 PM
To: dan () geer org; dailydave () lists immunitysec com
Subject: Re: [Dailydave] luckily, there are no dumb questions

 

If memory servers me right, Alpha only supported to "rings" and
therefore only 2 was used on Intel as well.

/andreas


-----Original Message-----
From: dailydave-bounces () lists immunitysec com on behalf of dan () geer org
Sent: Thu 6/7/2007 12:30 PM
To: dailydave () lists immunitysec com
Subject: [Dailydave] luckily, there are no dumb questions


Luckily, there are no dumb questions or this would
likely be one.

How is it so that MS Windows uses only Rings 0 & 3?
An engineering answer, a marketing answer, and/or
an historical answer would be welcome.  Don't know
why I never thought to ask before, but I'm asking
now.  (And if I'm really wrong, please tell me what
uses 1|2.)

Bemusedly,

--dan

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