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Re: big-little

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From "Andy \"Krazy\" Glew" <andy@SPAM.comp-arch.net>
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Subject Re: big-little
References <j7pu4q$ndv$1@USTR-NEWS.TR.UNISYS.COM> <j82d3u$6lt$1@news.albasani.net> <j832aa$og0$1@gosset.csi.cam.ac.uk> <j84sm2$g94$1@news.albasani.net> <3r2dnXmsb44LVi_TnZ2dnUVZ87-dnZ2d@telenor.com>
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On 11/3/2011 9:30 AM, Morten Reistad wrote:
> In article<j84sm2$g94$1@news.albasani.net>, BGB<cr88192@hotmail.com>  wrote:
>> On 10/23/2011 11:58 PM, nmm1@cam.ac.uk wrote:
>>> In article<j82d3u$6lt$1@news.albasani.net>, BGB<cr88192@hotmail.com>   wrote:
>>>>>>
>
>> I don't think mismatched clock rates will break either the operation of
>> mutexes, of critical sections in general, or of things like message queues.
>
> We already have mismatched clock rates. The current crop of processors
> change speed all the time. Just go look with "Powertop" or some other
> utility.

AFAIK all of the current generation of multicore chips have all or most 
of the processors running at the same basic clock frequency at all 
times.  I.e. they are all in the same frequency (and voltage) planes.

(I should qualify: symmetric multicore.  Not ARM big.LITTLE, Nvidia's 
4+1, or the various SOCs with different cores.)

I believe that one of the earliest AMD multicore chips allowed the OS to 
set each of the processors to a different frequency.  But I believe they 
backed away from it, as everyone else seems to have.

Why? I do not know.  I conjecture that the overhead of truly 
asynchronous clocks, or even clocks of the same frequency but in no 
guaranteed phase relationship, was too high.  But I also know that 
software providers complained a lot about the possibility of differing 
clock rates.  Heck, they wanted all of the CPUs to be guaranteed to be 
of the same stepping, back when it was common to have different CU chips.

It is possible that they allow the processors to run at different clock 
rates by adjusting clock dividers, or p/q rational ratios.

However, most of the examples of stuff like Turbo mode shows all of the 
clock frequencies the same.

I must admit that I wonder if this is true for some of the bigger 12 and 
16 core chips.  I would expect, and chip photos seem to say, that these 
are sometimes just pastiches of several 4 core modules.  This suggests 
that they could have different clocks, or, if driven by the same clock, 
that they may still have iffy phase drift.

--

But as for the real question: I doubt that any good software would be 
broken by differing clock rates.

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big-little timcaffrey@aol.com (Tim McCaffrey) - 2011-10-20 19:51 +0000
  Re: big-little Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-10-20 22:35 +0200
    Re: big-little Mark Thorson <nospam@sonic.net> - 2011-10-20 14:18 -0800
      Re: big-little nmm1@cam.ac.uk - 2011-10-21 07:54 +0100
        Re: big-little David Kanter <dkanter@gmail.com> - 2011-11-09 01:06 -0800
          Re: big-little nmm1@cam.ac.uk - 2011-11-09 11:07 +0000
      Re: big-little Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-10-21 09:25 +0200
      Re: big-little EricP <ThatWouldBeTelling@thevillage.com> - 2011-10-21 11:07 -0400
        Re: big-little timcaffrey@aol.com (Tim McCaffrey) - 2011-10-21 16:28 +0000
          Re: big-little nmm1@cam.ac.uk - 2011-10-21 17:07 +0100
          Re: big-little EricP <ThatWouldBeTelling@thevillage.com> - 2011-10-21 13:25 -0400
            Re: big-little timcaffrey@aol.com (Tim McCaffrey) - 2011-10-21 19:45 +0000
              Re: big-little EricP <ThatWouldBeTelling@thevillage.com> - 2011-10-22 14:44 -0400
          Re: big-little ChrisQ <meru@devnull.com> - 2011-10-22 16:57 +0000
            Re: big-little nmm1@cam.ac.uk - 2011-10-22 17:40 +0100
              Re: big-little ChrisQ <meru@devnull.com> - 2011-10-23 14:39 +0000
                Re: big-little nmm1@cam.ac.uk - 2011-10-23 16:11 +0100
                Re: big-little ChrisQ <meru@devnull.com> - 2011-10-23 17:44 +0000
                Re: big-little nmm1@cam.ac.uk - 2011-10-23 18:46 +0100
                Re: big-little Thomas Womack <twomack@chiark.greenend.org.uk> - 2011-10-23 19:30 +0100
                Re: big-little nmm1@cam.ac.uk - 2011-10-23 19:59 +0100
                Re: big-little BGB <cr88192@hotmail.com> - 2011-10-23 13:21 -0700
                Re: big-little Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-10-23 20:38 +0200
                Re: big-little nmm1@cam.ac.uk - 2011-10-23 22:38 +0100
                Re: big-little BGB <cr88192@hotmail.com> - 2011-10-23 17:56 -0700
                Re: big-little nmm1@cam.ac.uk - 2011-10-24 07:58 +0100
                Re: big-little BGB <cr88192@hotmail.com> - 2011-10-24 16:34 -0700
                Re: big-little nmm1@cam.ac.uk - 2011-10-25 08:09 +0100
                Re: big-little Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-10-25 14:52 +0200
                Re: big-little nmm1@cam.ac.uk - 2011-10-25 17:28 +0100
                Re: big-little BGB <cr88192@hotmail.com> - 2011-10-25 13:06 -0700
                Re: big-little BGB <cr88192@hotmail.com> - 2011-10-25 15:22 -0700
                Re: big-little "Andy \"Krazy\" Glew" <andy@SPAM.comp-arch.net> - 2011-10-25 19:47 -0700
                Re: big-little nmm1@cam.ac.uk - 2011-10-26 08:09 +0100
                Re: big-little Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-10-26 12:06 +0200
                Re: big-little nmm1@cam.ac.uk - 2011-10-26 10:47 +0100
                Re: big-little Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-10-26 11:58 +0200
                Re: big-little nmm1@cam.ac.uk - 2011-10-26 10:44 +0100
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-26 03:45 -0700
                Re: big-little nmm1@cam.ac.uk - 2011-10-26 11:45 +0100
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-26 09:15 -0700
                Re: big-little "Andy \"Krazy\" Glew" <andy@SPAM.comp-arch.net> - 2011-10-26 12:51 -0700
                Re: big-little Andrew Reilly <areilly---@bigpond.net.au> - 2011-10-26 11:45 +0000
                Re: big-little nmm1@cam.ac.uk - 2011-10-26 15:42 +0100
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-26 09:07 -0700
                Re: big-little "Andy \"Krazy\" Glew" <andy@SPAM.comp-arch.net> - 2011-10-26 12:53 -0700
                Re: big-little nmm1@cam.ac.uk - 2011-10-26 21:05 +0100
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-26 13:20 -0700
                Re: big-little "Andy \"Krazy\" Glew" <andy@SPAM.comp-arch.net> - 2011-10-26 17:55 -0700
                Re: big-little nmm1@cam.ac.uk - 2011-10-27 09:10 +0100
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-27 01:34 -0700
                Re: big-little nmm1@cam.ac.uk - 2011-10-27 10:29 +0100
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-27 04:28 -0700
                Re: big-little EricP <ThatWouldBeTelling@thevillage.com> - 2011-10-27 12:22 -0400
                Re: big-little timcaffrey@aol.com (Tim McCaffrey) - 2011-10-27 18:08 +0000
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-27 11:50 -0700
                Re: big-little Jean-Marc Bourguet <jm@bourguet.org> - 2011-10-27 14:10 +0200
                Re: big-little nmm1@cam.ac.uk - 2011-10-27 17:58 +0100
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-26 13:15 -0700
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-27 04:10 -0700
                Re: big-little MitchAlsup <MitchAlsup@aol.com> - 2011-10-27 14:04 -0700
                Re: big-little nmm1@cam.ac.uk - 2011-10-27 23:07 +0100
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-27 15:58 -0700
                Re: big-little Rick Jones <rick.jones2@hp.com> - 2011-10-27 22:57 +0000
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-27 16:39 -0700
                Re: big-little Rick Jones <rick.jones2@hp.com> - 2011-10-28 00:16 +0000
                Re: big-little nmm1@cam.ac.uk - 2011-10-28 09:52 +0100
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-28 07:01 -0700
                Re: big-little Rick Jones <rick.jones2@hp.com> - 2011-10-28 16:45 +0000
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-29 13:13 -0700
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-30 03:36 -0700
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-30 03:55 -0700
                Re: big-little MitchAlsup <MitchAlsup@aol.com> - 2011-10-28 11:15 -0700
                Re: big-little nmm1@cam.ac.uk - 2011-10-28 20:01 +0100
                Re: big-little timcaffrey@aol.com (Tim McCaffrey) - 2011-10-29 17:46 +0000
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-29 11:30 -0700
                Re: big-little nmm1@cam.ac.uk - 2011-10-29 20:02 +0100
                Re: big-little MitchAlsup <MitchAlsup@aol.com> - 2011-10-29 13:09 -0700
                Re: big-little "Paul A. Clayton" <paaronclayton@gmail.com> - 2011-10-29 17:42 -0700
                Re: big-little nmm1@cam.ac.uk - 2011-10-30 08:16 +0000
                Re: big-little MitchAlsup <MitchAlsup@aol.com> - 2011-11-04 10:06 -0700
                Re: big-little "Paul A. Clayton" <paaronclayton@gmail.com> - 2011-11-04 15:19 -0700
                Re: big-little nmm1@cam.ac.uk - 2011-11-05 09:13 +0000
                Re: big-little "Andy \"Krazy\" Glew" <andy@SPAM.comp-arch.net> - 2011-11-05 09:03 -0700
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-26 13:38 -0700
                Re: big-little Robert Wessel <robertwessel2@yahoo.com> - 2011-10-26 18:44 -0500
                Re: big-little Michael S <already5chosen@yahoo.com> - 2011-10-26 17:05 -0700
                Re: big-little Robert Wessel <robertwessel2@yahoo.com> - 2011-10-26 21:03 -0500
                Re: big-little EricP <ThatWouldBeTelling@thevillage.com> - 2011-10-26 14:37 -0400
                Re: big-little EricP <ThatWouldBeTelling@thevillage.com> - 2011-10-26 15:38 -0400
                Re: big-little EricP <ThatWouldBeTelling@thevillage.com> - 2011-10-26 16:06 -0400
                Re: big-little BGB <cr88192@hotmail.com> - 2011-10-27 00:15 -0700
                Re: big-little Morten Reistad <first@last.name> - 2011-11-03 17:30 +0100
                Re: big-little "Andy \"Krazy\" Glew" <andy@SPAM.comp-arch.net> - 2011-11-03 20:45 -0700
                Re: big-little Thomas Womack <twomack@chiark.greenend.org.uk> - 2011-11-04 11:13 +0000
                Re: big-little MitchAlsup <MitchAlsup@aol.com> - 2011-11-04 10:12 -0700
                Re: big-little BGB <cr88192@hotmail.com> - 2011-11-04 09:26 -0700
                Re: big-little EricP <ThatWouldBeTelling@thevillage.com> - 2011-11-05 11:32 -0400
                Re: big-little EricP <ThatWouldBeTelling@thevillage.com> - 2011-11-05 11:55 -0400
                Re: big-little BGB <cr88192@hotmail.com> - 2011-11-05 09:58 -0700
                Re: big-little Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-11-05 18:39 +0100
                Re: big-little BGB <cr88192@hotmail.com> - 2011-11-05 15:00 -0700
                Re: big-little wclodius@lost-alamos.pet (William Clodius) - 2011-11-05 18:43 -0600
                Re: big-little BGB <cr88192@hotmail.com> - 2011-11-05 19:46 -0700
                Re: big-little ChrisQ <meru@devnull.com> - 2011-11-11 12:31 +0000
                Re: big-little BGB <cr88192@hotmail.com> - 2011-11-11 12:39 -0700
                Re: big-little Chris Gray <cg@GraySage.com> - 2011-11-11 13:28 -0700
                Re: big-little BGB <cr88192@hotmail.com> - 2011-11-11 18:03 -0700
                Re: big-little Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-11-12 18:25 +0100
                Re: big-little BGB <cr88192@hotmail.com> - 2011-11-12 12:02 -0700
                cost of prolog/epilog (was: big-little) Kalle Olavi Niemitalo <kon@iki.fi> - 2011-11-12 22:57 +0200
                Re: cost of prolog/epilog Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-11-12 22:47 +0100
                Re: cost of prolog/epilog anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-11-14 09:45 +0000
                Re: cost of prolog/epilog Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-11-14 12:28 +0100
                Re: cost of prolog/epilog anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-11-15 16:48 +0000
                Re: cost of prolog/epilog Stefan Monnier <monnier@iro.umontreal.ca> - 2011-11-15 21:35 -0500
                Re: cost of prolog/epilog Bakul Shah <usenet@bitblocks.com> - 2011-11-16 02:41 -0800
                Re: cost of prolog/epilog nmm1@cam.ac.uk - 2011-11-16 18:14 +0000
                Re: cost of prolog/epilog BGB <cr88192@hotmail.com> - 2011-11-16 16:50 -0700
                Re: cost of prolog/epilog BGB <cr88192@hotmail.com> - 2011-11-14 17:00 -0700
                Re: cost of prolog/epilog torbenm@diku.dk (Torben Ægidius Mogensen) - 2011-11-15 10:26 +0100
                Re: cost of prolog/epilog BGB <cr88192@hotmail.com> - 2011-11-15 09:41 -0700
                Re: cost of prolog/epilog anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-11-15 16:40 +0000
                Re: cost of prolog/epilog Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-11-15 12:44 +0100
                Re: cost of prolog/epilog BGB <cr88192@hotmail.com> - 2011-11-15 09:01 -0700
                Re: cost of prolog/epilog Chris Gray <cg@GraySage.com> - 2011-11-15 15:18 -0700
                Re: cost of prolog/epilog BGB <cr88192@hotmail.com> - 2011-11-15 21:56 -0700
                Re: cost of prolog/epilog Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-11-16 09:21 +0100
                Re: cost of prolog/epilog anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-11-16 09:30 +0000
                Re: cost of prolog/epilog John Levine <johnl@iecc.com> - 2011-11-16 10:05 +0000
                Re: cost of prolog/epilog Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-11-16 11:08 +0100
                Re: cost of prolog/epilog Chris Gray <cg@GraySage.com> - 2011-11-16 16:29 -0700
                Re: cost of prolog/epilog BGB <cr88192@hotmail.com> - 2011-11-16 11:22 -0700
                Re: cost of prolog/epilog anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-11-17 13:27 +0000
                Re: cost of prolog/epilog BGB <cr88192@hotmail.com> - 2011-11-17 10:30 -0700
                Re: cost of prolog/epilog torbenm@diku.dk (Torben Ægidius Mogensen) - 2011-11-17 11:21 +0100
                Re: cost of prolog/epilog Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-11-17 11:56 +0100
                Re: cost of prolog/epilog timcaffrey@aol.com (Tim McCaffrey) - 2011-11-17 20:27 +0000
                Re: cost of prolog/epilog torbenm@diku.dk (Torben Ægidius Mogensen) - 2011-11-18 10:57 +0100
                Re: cost of prolog/epilog BGB <cr88192@hotmail.com> - 2011-11-17 10:42 -0700
                Re: cost of prolog/epilog (was: big-little) "Paul A. Clayton" <paaronclayton@gmail.com> - 2011-11-12 14:05 -0800
                Re: cost of prolog/epilog (was: big-little) Bernd Paysan <bernd.paysan@gmx.de> - 2011-11-18 02:39 +0100
                Re: cost of prolog/epilog torbenm@diku.dk (Torben Ægidius Mogensen) - 2011-11-18 10:59 +0100
                Re: cost of prolog/epilog Bernd Paysan <bernd.paysan@gmx.de> - 2011-11-18 22:06 +0100
                Re: cost of prolog/epilog (was: big-little) mac <acolvin@efunct.com> - 2011-11-20 23:01 +0000
                Re: cost of prolog/epilog Chris Gray <cg@GraySage.com> - 2011-11-13 13:35 -0700
                Re: big-little wclodius@lost-alamos.pet (William Clodius) - 2011-11-11 22:13 -0700
                Re: big-little BGB <cr88192@hotmail.com> - 2011-11-11 23:43 -0700
                Re: big-little Chris Gray <cg@GraySage.com> - 2011-11-12 14:08 -0700
                Re: big-little BGB <cr88192@hotmail.com> - 2011-11-12 19:10 -0700
                Re: big-little Chris Gray <cg@GraySage.com> - 2011-11-13 13:40 -0700
                Re: big-little Bakul Shah <usenet@bitblocks.com> - 2011-11-13 14:49 -0800
                Re: big-little BGB <cr88192@hotmail.com> - 2011-11-13 18:51 -0700
                Re: big-little Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-10-24 10:12 +0200
                Re: big-little Stefan Monnier <monnier@iro.umontreal.ca> - 2011-10-24 12:11 -0400
                Re: big-little "Paul A. Clayton" <paaronclayton@gmail.com> - 2011-10-24 10:28 -0700
                Re: big-little nospam@ab-katrinedal.dk (Niels Jørgen Kruse) - 2011-10-24 19:38 +0200
                Re: big-little Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-10-24 21:02 +0200
                Re: big-little "Paul A. Clayton" <paaronclayton@gmail.com> - 2011-10-23 12:02 -0700
        Re: big-little Morten Reistad <first@last.name> - 2011-11-03 00:51 +0100
    Re: big-little "Paul A. Clayton" <paaronclayton@gmail.com> - 2011-10-20 16:59 -0700
      Re: big-little Anne & Lynn Wheeler <lynn@garlic.com> - 2011-10-20 21:13 -0400
      Re: big-little nmm1@cam.ac.uk - 2011-10-21 08:01 +0100
        Re: big-little "Paul A. Clayton" <paaronclayton@gmail.com> - 2011-10-21 05:39 -0700
        Re: big-little torbenm@diku.dk (Torben Ægidius Mogensen) - 2011-10-24 10:18 +0200
      Re: big-little Pedro Pereira <ppereira@grupopie.com> - 2011-10-21 10:40 +0100
        Re: big-little Paul Gotch <paulg@at-cantab-dot.net> - 2011-10-21 12:42 +0100
    Re: big-little nik Simpson <nik_s@knology.net> - 2011-10-21 11:00 -0500
  Re: big-little Rick Jones <rick.jones2@hp.com> - 2011-10-20 21:13 +0000
    Re: big-little timcaffrey@aol.com (Tim McCaffrey) - 2011-10-20 21:43 +0000
    Re: big-little Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-10-21 09:23 +0200
      Re: big-little Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-10-21 14:35 +0200
        Re: big-little Rick Jones <rick.jones2@hp.com> - 2011-10-21 17:15 +0000
      Re: big-little BGB <cr88192@hotmail.com> - 2011-10-21 16:41 -0700
  Re: big-little jacko <jackokring@gmail.com> - 2011-10-26 14:12 -0700

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