Re: x86 real mode

From	Don Y <this@is.not.me.com>
Newsgroups	comp.arch.embedded
Subject	Re: x86 real mode
Date	2014-10-20 08:15 -0700
Organization	Aioe.org NNTP Server
Message-ID	<m23901$kd8$1@speranza.aioe.org> (permalink)
References	(2 earlier) <m1s2r2$hib$1@speranza.aioe.org> <dv444ahac3uln4s2nto94duo921i7fh35s@4ax.com> <m1taj5$uur$1@speranza.aioe.org> <m1v207$aq5$1@speranza.aioe.org> <0r694a1e7g2kdb59b793d13t6vqqfeuq4n@4ax.com>

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Hi George,

On 10/19/2014 10:35 PM, George Neuner wrote:
> On Sat, 18 Oct 2014 17:52:08 -0700, Don Y <this@is.not.me.com> wrote:
>
>> Effectively, a "program" only executes in two rings -- a
>> "user" ring ("4") and the "system" ring ("0").
>>
>> As with many technical issues, coming up with the "right number"
>> is hard.  Too few and you lose the value they present.  Too
>> many and a "program" spends too much time crossing protection domains
>> ("for little value")
>
> I think there's a clear need for at least 4 general protection zones:
> kernel, device driver, OS services and user applications.  Beyond that
> you're getting into user politics.
>
> IIRC NT 3.x and OS/2 1.x/2.x did use rings 0, 1 and 3.  NT 4 retreated
> to using only rings 0 and 3, and I *think* OS/2 Warp versions did
> also.  And x86 now has dropped segmentation altogether in 64-bit mode
> so the rings aren't even available.

I think the multics folks looked at this with an attitude of
"if these features were free, what would be the 'right/best' way
of designing a complex system".

I.e., a *user program* could benefit from the same schemes that
benefit the "system".  So, let's extend the ring concept into
user-land!

Of course, crossing protection boundaries is not free.  And, designing
with that sort of strict structure takes considerably more planning than
the ad hoc approaches so common!  :-/

I'm sure I've got a copy of Organick here, someplace...  but, I'd wager
few (if any!) user-land programs took advantage of any of this!  [A
possible exception *may* have been The Consistent System]

As we've discussed before, I really think just two execution levels
are adequate for most systems **if** you have fine-grained control
of access to peripherals (whether they are memory- or I/O-mapped).

Thread

x86 real mode Don Y <this@is.not.me.com> - 2014-10-17 07:23 -0700
  Re: x86 real mode Arlet Ottens <usenet+5@c-scape.nl> - 2014-10-17 16:31 +0200
    Re: x86 real mode Don Y <this@is.not.me.com> - 2014-10-17 07:45 -0700
      Re: x86 real mode Arlet Ottens <usenet+5@c-scape.nl> - 2014-10-17 16:53 +0200
        Re: x86 real mode Don Y <this@is.not.me.com> - 2014-10-17 08:28 -0700
          Re: x86 real mode Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2014-10-17 18:35 +0300
          Re: x86 real mode Arlet Ottens <usenet+5@c-scape.nl> - 2014-10-17 17:36 +0200
            Re: x86 real mode Don Y <this@is.not.me.com> - 2014-10-17 13:54 -0700
              Re: x86 real mode Grant Edwards <invalid@invalid.invalid> - 2014-10-17 21:02 +0000
                Re: x86 real mode Don Y <this@is.not.me.com> - 2014-10-17 14:54 -0700
              Re: x86 real mode upsidedown@downunder.com - 2014-10-18 10:09 +0300
          Re: x86 real mode Grant Edwards <invalid@invalid.invalid> - 2014-10-17 16:11 +0000
      Re: x86 real mode Stefan Reuther <stefan.news@arcor.de> - 2014-10-17 18:37 +0200
      Re: x86 real mode Les Cargill <lcargill99@comcast.com> - 2014-10-17 12:58 -0500
  Re: x86 real mode David Brown <david.brown@hesbynett.no> - 2014-10-17 16:52 +0200
    Re: x86 real mode glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-10-17 16:45 +0000
  Re: x86 real mode Robert Wessel <robertwessel2@yahoo.com> - 2014-10-17 10:03 -0500
  Re: x86 real mode Grant Edwards <invalid@invalid.invalid> - 2014-10-17 16:07 +0000
  Re: x86 real mode upsidedown@downunder.com - 2014-10-17 19:57 +0300
  Re: x86 real mode Les Cargill <lcargill99@comcast.com> - 2014-10-17 12:57 -0500
  Re: x86 real mode Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2014-10-17 21:18 +0300
    Re: x86 real mode glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-10-17 21:48 +0000
      Re: x86 real mode Don Y <this@is.not.me.com> - 2014-10-17 15:06 -0700
        Re: x86 real mode glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-10-17 22:25 +0000
          Re: x86 real mode Don Y <this@is.not.me.com> - 2014-10-17 15:39 -0700
            Re: x86 real mode George Neuner <gneuner2@comcast.net> - 2014-10-17 22:47 -0400
              Re: x86 real mode Don Y <this@is.not.me.com> - 2014-10-17 21:10 -0700
                Re: x86 real mode upsidedown@downunder.com - 2014-10-18 11:32 +0300
            Re: x86 real mode upsidedown@downunder.com - 2014-10-18 11:10 +0300
              Re: x86 real mode Don Y <this@is.not.me.com> - 2014-10-18 08:20 -0700
                Re: x86 real mode upsidedown@downunder.com - 2014-10-18 20:34 +0300
                Re: x86 real mode Don Y <this@is.not.me.com> - 2014-10-18 12:53 -0700
          Re: x86 real mode upsidedown@downunder.com - 2014-10-18 10:30 +0300
          Re: x86 real mode David Brown <david.brown@hesbynett.no> - 2014-10-18 20:22 +0200
      Re: x86 real mode upsidedown@downunder.com - 2014-10-18 10:22 +0300
        Re: x86 real mode glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-10-18 09:06 +0000
          Re: x86 real mode Robert Wessel <robertwessel2@yahoo.com> - 2014-10-18 08:43 -0500
          Re: x86 real mode Gerd Brix <gbrix@gmx.eu> - 2014-10-18 16:39 +0200
          Re: x86 real mode Don Y <this@is.not.me.com> - 2014-10-18 17:52 -0700
            Re: x86 real mode George Neuner <gneuner2@comcast.net> - 2014-10-20 01:35 -0400
              Re: x86 real mode upsidedown@downunder.com - 2014-10-20 10:14 +0300
                Re: x86 real mode George Neuner <gneuner2@comcast.net> - 2014-10-20 14:12 -0400
              Re: x86 real mode Don Y <this@is.not.me.com> - 2014-10-20 08:15 -0700
    Re: x86 real mode Les Cargill <lcargill99@comcast.com> - 2014-10-17 18:39 -0500
      Re: x86 real mode Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2014-10-18 10:46 +0300
  Re: x86 real mode George Neuner <gneuner2@comcast.net> - 2014-10-17 15:29 -0400
    Re: x86 real mode Don Y <this@is.not.me.com> - 2014-10-17 14:32 -0700
      Re: x86 real mode Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2014-10-18 00:09 +0200
        Re: x86 real mode glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-10-17 22:31 +0000
          Re: x86 real mode upsidedown@downunder.com - 2014-10-18 12:04 +0300
            Re: x86 real mode glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-10-18 23:22 +0000
            Re: x86 real mode Don Y <this@is.not.me.com> - 2014-10-18 20:59 -0700
      Re: x86 real mode upsidedown@downunder.com - 2014-10-18 11:53 +0300
        Re: x86 real mode Don Y <this@is.not.me.com> - 2014-10-18 09:34 -0700
    Re: x86 real mode glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-10-17 22:00 +0000
      Re: x86 real mode Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2014-10-18 00:26 +0200
        Re: x86 real mode glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-10-17 22:36 +0000
      Re: x86 real mode George Neuner <gneuner2@comcast.net> - 2014-10-17 21:45 -0400
        Re: x86 real mode glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-10-18 03:26 +0000
          Re: x86 real mode Robert Wessel <robertwessel2@yahoo.com> - 2014-10-17 23:26 -0500
            Re: x86 real mode glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-10-18 05:42 +0000
          Re: x86 real mode Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2014-10-18 10:53 +0300
            Re: x86 real mode glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-10-18 09:12 +0000
        Re: x86 real mode Robert Wessel <robertwessel2@yahoo.com> - 2014-10-17 22:40 -0500
      Re: x86 real mode George Neuner <gneuner2@comcast.net> - 2014-10-17 22:07 -0400

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