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Re: If Memory Had Been Cheaper

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Peter Flass <peter_flass@yahoo.com> writes:
> Was that you? Doesn’t VM use a “sweep” algorithm? Process all requests that
> will keep the arm moving in one direction, then reverse and process all the
> requests in the other.

Original CP67 was FIFO, at the univ. as undergraduate in the 60s, I
changed it to ordered seek ... also did chained requests for paging in
one channel program (ordered by rotation, if didn't require seek)
... instead of separate channel program/SIO for every page (which was
one of the things retained for vm370, but a lot of other stuff was
dropped and/or at least drastically simplified).

for 370/125 ... the controller had real-time rotational position, there
was delay for rotation and delay for seek arm ... there were some
situations where could do a further seek delay might be less than closer
arm rotation delay ... it was possible because the whole I/O request
queue was exposed to the controller ... and could do real-time
reordering ... not only knowing the disk arm position but also the
real-time rotational position.

-- 
virtualization experience starting Jan1968, online at home since Mar1970

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If Memory Had Been Cheaper Quadibloc <jsavard@ecn.ab.ca> - 2020-08-06 14:24 -0700
  Re: If Memory Had Been Cheaper Terry Kennedy <terry-groups@glaver.org> - 2020-08-06 16:59 -0700
    Re: If Memory Had Been Cheaper Quadibloc <jsavard@ecn.ab.ca> - 2020-08-06 17:22 -0700
    Re: If Memory Had Been Cheaper Anne & Lynn Wheeler <lynn@garlic.com> - 2020-08-08 16:10 -1000
      Re: If Memory Had Been Cheaper Terry Kennedy <terry-groups@glaver.org> - 2020-08-08 21:07 -0700
      Re: If Memory Had Been Cheaper Peter Flass <peter_flass@yahoo.com> - 2020-08-09 10:07 -0700
        Re: If Memory Had Been Cheaper Anne & Lynn Wheeler <lynn@garlic.com> - 2020-08-09 11:04 -1000
          Re: If Memory Had Been Cheaper Anne & Lynn Wheeler <lynn@garlic.com> - 2020-08-09 12:03 -1000
            Re: If Memory Had Been Cheaper Peter Flass <peter_flass@yahoo.com> - 2020-08-09 15:30 -0700
  Re: If Memory Had Been Cheaper J. Clarke <jclarke.873638@gmail.com> - 2020-08-07 10:24 -0400
    Re: If Memory Had Been Cheaper timcaffrey420@gmail.com - 2020-08-07 11:26 -0700
      Re: If Memory Had Been Cheaper timcaffrey420@gmail.com - 2020-08-07 11:33 -0700
        Re: If Memory Had Been Cheaper Terry Kennedy <terry-groups@glaver.org> - 2020-08-07 13:30 -0700
      Re: If Memory Had Been Cheaper Peter Flass <peter_flass@yahoo.com> - 2020-08-07 11:39 -0700
      Re: If Memory Had Been Cheaper drb@ihatespam.msu.edu (Dennis Boone) - 2020-08-07 14:11 -0500
        Re: If Memory Had Been Cheaper Quadibloc <jsavard@ecn.ab.ca> - 2020-08-07 12:35 -0700
          Re: If Memory Had Been Cheaper Quadibloc <jsavard@ecn.ab.ca> - 2020-08-07 12:37 -0700
            Re: If Memory Had Been Cheaper J. Clarke <jclarke.873638@gmail.com> - 2020-08-08 13:23 -0400
        Re: If Memory Had Been Cheaper Anne & Lynn Wheeler <lynn@garlic.com> - 2020-08-08 16:29 -1000
      Re: If Memory Had Been Cheaper J. Clarke <jclarke.873638@gmail.com> - 2020-08-08 13:21 -0400
    Re: If Memory Had Been Cheaper Peter Flass <peter_flass@yahoo.com> - 2020-08-07 11:31 -0700
  Re: If Memory Had Been Cheaper Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2020-08-07 10:05 -0600
    Re: If Memory Had Been Cheaper Quadibloc <jsavard@ecn.ab.ca> - 2020-08-08 14:23 -0700
    Re: If Memory Had Been Cheaper undefined Hancock-4 <hancock4@bbs.cpcn.com> - 2020-08-15 11:42 -0700
      Re: If Memory Had Been Cheaper Quadibloc <jsavard@ecn.ab.ca> - 2020-08-15 21:48 -0700
        Re: If Memory Had Been Cheaper undefined Hancock-4 <hancock4@bbs.cpcn.com> - 2021-07-07 12:36 -0700
          Re: If Memory Had Been Cheaper J. Clarke <jclarke.873638@gmail.com> - 2021-07-07 17:03 -0400
            Re: If Memory Had Been Cheaper Robin Vowels <robin.vowels@gmail.com> - 2021-07-07 23:13 -0700
              Re: If Memory Had Been Cheaper Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2021-07-08 09:51 -0600
              Re: If Memory Had Been Cheaper char <char@code.ord> - 2021-07-08 17:56 -0500
            Re: If Memory Had Been Cheaper Quadibloc <jsavard@ecn.ab.ca> - 2021-07-08 09:31 -0700
              Re: If Memory Had Been Cheaper Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2021-07-08 18:14 +0000
                Re: If Memory Had Been Cheaper char <char@code.ord> - 2021-07-08 18:00 -0500
            Re: If Memory Had Been Cheaper undefined Hancock-4 <hancock4@bbs.cpcn.com> - 2021-07-13 15:21 -0700
            Re: If Memory Had Been Cheaper undefined Hancock-4 <hancock4@bbs.cpcn.com> - 2021-07-16 11:13 -0700
              Re: If Memory Had Been Cheaper J. Clarke <jclarke.873638@gmail.com> - 2021-07-16 17:20 -0400
                Re: If Memory Had Been Cheaper undefined Hancock-4 <hancock4@bbs.cpcn.com> - 2021-07-20 12:08 -0700
                Re: If Memory Had Been Cheaper Vir Campestris <vir.campestris@invalid.invalid> - 2021-07-20 21:30 +0100
                Re: If Memory Had Been Cheaper Quadibloc <jsavard@ecn.ab.ca> - 2021-07-22 04:09 -0700
                Re: If Memory Had Been Cheaper Thomas Koenig <tkoenig@netcologne.de> - 2021-07-22 13:51 +0000
                Re: If Memory Had Been Cheaper Quadibloc <jsavard@ecn.ab.ca> - 2021-07-22 14:50 -0700
          Re: If Memory Had Been Cheaper Ahem A Rivet's Shot <steveo@eircom.net> - 2021-07-07 22:20 +0100
          Re: If Memory Had Been Cheaper Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2021-07-07 18:52 -0600
            Re: If Memory Had Been Cheaper undefined Hancock-4 <hancock4@bbs.cpcn.com> - 2021-07-13 15:15 -0700
              Re: If Memory Had Been Cheaper Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2021-07-14 00:02 +0000
              Re: If Memory Had Been Cheaper J. Clarke <jclarke.873638@gmail.com> - 2021-07-13 21:30 -0400
          Re: If Memory Had Been Cheaper Vir Campestris <vir.campestris@invalid.invalid> - 2021-07-11 21:31 +0100
      Re: If Memory Had Been Cheaper JimP <chucktheouch@gmail.com> - 2020-08-16 11:15 -0500
        Re: If Memory Had Been Cheaper hancock4@bbs.cpcn.com - 2020-08-17 12:36 -0700
        Re: If Memory Had Been Cheaper Quadibloc <jsavard@ecn.ab.ca> - 2020-08-18 02:04 -0700
          Re: If Memory Had Been Cheaper JimP <chucktheouch@gmail.com> - 2020-08-19 07:53 -0500
            Re: If Memory Had Been Cheaper Robert Swindells <rjs@fdy2.co.uk> - 2020-08-19 14:15 +0000
              Re: If Memory Had Been Cheaper JimP <chucktheouch@gmail.com> - 2020-08-19 10:51 -0500
  Re: If Memory Had Been Cheaper undefined Hancock-4 <hancock4@bbs.cpcn.com> - 2020-08-15 11:39 -0700
    Re: If Memory Had Been Cheaper Quadibloc <jsavard@ecn.ab.ca> - 2020-08-15 21:54 -0700
      Re: If Memory Had Been Cheaper gah4 <gah4@u.washington.edu> - 2021-07-27 22:58 -0700
    Re: If Memory Had Been Cheaper David Lesher <wb8foz@panix.com> - 2020-08-16 21:44 +0000

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