Or use a PLB

By: dmcq (dmcq.delete@this.fano.co.uk), September 28, 2021 6:45 am
Room: Moderated Discussions
Adrian (a.delete@this.acm.org) on September 27, 2021 10:59 pm wrote:
> Adrian (a.delete@this.acm.org) on September 27, 2021 10:40 pm wrote:
> > David Hess (davidwhess.delete@this.gmail.com) on September 27, 2021 11:35 am wrote:
> > > blaine (myname.delete@this.acm.org) on September 26, 2021 11:19 pm wrote:
> > > >
> > > > As someone who was there: Morse was under severe constraints in design of the 8086.
> > > > I would not read anything into segments but as an expedient under constraints.
> > >
> > > I will add as an experienced 8080 and Z80 programmer at the
> > > time, the 8086 segmenting scheme was seen as a great
> > > improvement over contemporary developing solutions. Its
> > > limitations only became a problem later when single
> > > data structures exceeded the size of the entire 64 kilobyte
> > > address range of the previous generation of processors,
> > > and the alternatives (Zilog, others), except for a single larger address range (68000), were worse.
> > >
> >
> >
> > The 1978 Intel 8086 segmenting scheme was a great improvement
> > not only over the existing microprocesors with a
> > 16-bit address space, but also over what was available for the most popular minicomputers, i.e. DEC PDP-11.
> >
> > DEC PDP-11 extended its 16-bit address space to a 22-bit address
> > space (i.e. 4 MB) using a very primitive paging scheme.
> >
> > Paging in PDP-11 and similar minicomputers had nothing to do with paging in VAX, 80386 and similar
> > CPUs, where it was used for dynamic relocation, memory protection and virtual memory.
> >
> >
> > Paging in PDP-11 was primarily only a method for address space extension, which was far more inconvenient
> > to use than the segments of 8086, which could start at any 16-byte aligned address in the memory and which
> > could be loaded together with in-segment pointers with a single instruction (JMP FAR, LDS, LES).
> >
> > In PDP-11 you could access simultaneously the equivalent of two 64 kB segments, a data segment and a
> > code segment, but whenever you needed to access data or code from another part of the memory switching
> > the right pages was a much more tedious and convoluted process than using far pointers with 8086.
> >
> > Also, the fact that 8086 had 4 simultaneously accessible segments instead of only
> > 2 reduced a lot the need of switching segments in comparison with PDP-11.
> >
> >
> I want to add that because of the difficulties of using the PDP-11 paging, in simpler
> operating systems, i.e. UNIX, paging was not used at all in user programs.
> UNIX processes were limited in size to what was accessible without switching pages, i.e. an
> up to 64 kB text segment and an up to 64 kB sum of the data, bss, stack and heap sizes.
> The entire up to 4 MB PDP-11 memory was used only by running concurrently many UNIX processes.
> On the other hand on Intel 8086 there was no problem e.g. to use a 512 kB array
> in your program, if you compiled it for the large or compact memory models.

When all this business about PDP and paging was started here I thought the DECsystem-10 was meant, not PDP-11! That had proper virtual memory and ran big time sharing systems. Well big for the time! ;-)
< Previous Post in ThreadNext Post in Thread >
TopicPosted ByDate
POWER10 SAP SD benchmarkanon22021/09/06 02:36 PM
  POWER10 SAP SD benchmarkDaniel B2021/09/07 01:31 AM
    "Cores" (and SPEC)Rayla2021/09/07 06:51 AM
      "Cores" (and SPEC)anon2021/09/07 02:56 PM
  POWER10 SAP SD benchmarkAnon2021/09/07 02:24 PM
    POWER10 SAP SD benchmarkAnon2021/09/07 02:27 PM
  Virtually tagged L1-cachessr2021/09/08 04:49 AM
    Virtually tagged L1-cachesdmcq2021/09/08 07:22 AM
      Virtually tagged L1-cachessr2021/09/08 07:56 AM
      Virtually tagged L1-cachesHugo Décharnes2021/09/08 07:58 AM
        Virtually tagged L1-cachessr2021/09/08 09:09 AM
          Virtually tagged L1-cachesHugo Décharnes2021/09/08 09:46 AM
            Virtually tagged L1-cachessr2021/09/08 10:35 AM
              Virtually tagged L1-cachesHugo Décharnes2021/09/08 11:23 AM
                Virtually tagged L1-cachessr2021/09/08 11:40 AM
                  Virtually tagged L1-cachesanon2021/09/09 02:16 AM
                    Virtually tagged L1-cachesKonrad Schwarz2021/09/10 04:19 AM
                      Virtually tagged L1-cachesHugo Décharnes2021/09/10 05:59 AM
                        Virtually tagged L1-cachesanon2021/09/14 02:17 AM
                          Virtually tagged L1-cachesdmcq2021/09/14 08:34 AM
                            Or use a PLB (NT)Paul A. Clayton2021/09/14 08:45 AM
                              Or use a PLBLinus Torvalds2021/09/14 02:27 PM
                                Or use a PLBanon2021/09/14 11:15 PM
                                  Or use a PLBMichael S2021/09/15 02:21 AM
                                    Or use a PLBdmcq2021/09/15 02:42 PM
                                      Or use a PLBKonrad Schwarz2021/09/16 03:24 AM
                                        Or use a PLBMichael S2021/09/16 09:13 AM
                                          Or use a PLB---2021/09/16 12:02 PM
                                  PLB referencePaul A. Clayton2021/09/18 01:35 PM
                                    PLB referenceMichael S2021/09/18 03:14 PM
                                      Demand paging/translation orthogonalPaul A. Clayton2021/09/19 06:33 AM
                                        Demand paging/translation orthogonalMichael S2021/09/19 08:10 AM
                                      PLB referenceCarson2021/09/20 09:19 PM
                                    PLB referencesr2021/09/20 05:02 AM
                                      PLB referenceMichael S2021/09/20 06:03 AM
                                        PLB referenceLinus Torvalds2021/09/20 11:10 AM
                                  Or use a PLBsr2021/09/20 03:32 AM
                              Or use a PLBsr2021/09/21 08:36 AM
                                Or use a PLBLinus Torvalds2021/09/21 09:04 AM
                                  Or use a PLBsr2021/09/21 09:48 AM
                                    Or use a PLBLinus Torvalds2021/09/21 12:55 PM
                                      Or use a PLBsr2021/09/22 05:55 AM
                                        Or use a PLBrwessel2021/09/22 06:09 AM
                                        Or use a PLBLinus Torvalds2021/09/22 10:50 AM
                                          Or use a PLBsr2021/09/22 12:00 PM
                                            Or use a PLBdmcq2021/09/22 03:07 PM
                                            Or use a PLBEtienne Lorrain2021/09/23 07:50 AM
                                          Or use a PLBanon22021/09/22 03:09 PM
                                            Or use a PLBdmcq2021/09/23 01:35 AM
                                          Or use a PLB2021/09/23 08:37 AM
                                            Or use a PLBLinus Torvalds2021/09/23 11:01 AM
                                              Or use a PLBgpd2021/09/24 02:59 AM
                                                Or use a PLBLinus Torvalds2021/09/24 09:45 AM
                                                  Or use a PLBdmcq2021/09/24 11:43 AM
                                                  Or use a PLBsr2021/09/25 09:19 AM
                                                    Or use a PLBLinus Torvalds2021/09/25 09:44 AM
                                                      Or use a PLBsr2021/09/25 10:11 AM
                                                        Or use a PLBLinus Torvalds2021/09/25 10:31 AM
                                                          Or use a PLBsr2021/09/25 10:52 AM
                                                            Or use a PLBLinus Torvalds2021/09/25 11:05 AM
                                                              Or use a PLBsr2021/09/25 11:23 AM
                                                                Or use a PLBrwessel2021/09/25 02:29 PM
                                                                  Or use a PLBsr2021/09/30 11:22 PM
                                                                    Or use a PLBrwessel2021/10/01 05:19 AM
                                                                      Or use a PLBDavid Hess2021/10/01 09:35 AM
                                                                        Or use a PLBrwessel2021/10/02 03:47 AM
                                                                      Or use a PLBsr2021/10/02 10:16 AM
                                                                        Or use a PLBrwessel2021/10/02 10:53 AM
                                                          Or use a PLBLinus Torvalds2021/09/25 10:57 AM
                                                            Or use a PLBsr2021/09/25 11:07 AM
                                                              Or use a PLBLinus Torvalds2021/09/25 11:21 AM
                                                                Or use a PLBsr2021/09/25 11:40 AM
                                                                  Or use a PLBnksingh2021/09/27 08:07 AM
                                                          Or use a PLB2021/09/27 08:02 AM
                                                            Or use a PLBLinus Torvalds2021/09/27 09:20 AM
                                                              Or use a PLBLinus Torvalds2021/09/27 11:58 AM
                                                                Or use a PLBdmcq2021/09/28 09:59 AM
                                              Or use a PLBsr2021/09/25 09:34 AM
                                                Or use a PLBrwessel2021/09/25 02:44 PM
                                                  Or use a PLBsr2021/10/01 12:04 AM
                                                    Or use a PLBrwessel2021/10/01 05:33 AM
                                                      I386 segmentation highlightssr2021/10/04 06:53 AM
                                                        I386 segmentation highlightsAdrian2021/10/04 08:53 AM
                                                          I386 segmentation highlightssr2021/10/04 09:19 AM
                                                        I386 segmentation highlightsrwessel2021/10/04 03:57 PM
                                                          I386 segmentation highlightssr2021/10/05 10:16 AM
                                                            I386 segmentation highlightsMichael S2021/10/05 11:27 AM
                                                            I386 segmentation highlightsrwessel2021/10/05 03:20 PM
                                                Or use a PLBJohnG2021/09/25 09:18 PM
                                              Or use a PLB2021/09/27 06:37 AM
                                                Or use a PLBHeikki Kultala2021/09/28 02:53 AM
                                                  Or use a PLBrwessel2021/09/28 06:29 AM
                                        Or use a PLBDavid Hess2021/09/23 05:00 PM
                                          Or use a PLBAdrian2021/09/24 12:21 AM
                                            Or use a PLBdmcq2021/09/25 11:41 AM
                                        Or use a PLBblaine2021/09/26 10:19 PM
                                          Or use a PLBDavid Hess2021/09/27 10:35 AM
                                            Or use a PLBblaine2021/09/27 04:19 PM
                                            Or use a PLBAdrian2021/09/27 09:40 PM
                                              Or use a PLBAdrian2021/09/27 09:59 PM
                                                Or use a PLBdmcq2021/09/28 06:45 AM
                                              Or use a PLBrwessel2021/09/28 06:45 AM
                                              Or use a PLBDavid Hess2021/09/28 11:50 AM
                                                Or use a PLBEtienne Lorrain2021/09/30 12:25 AM
                                                  Or use a PLBDavid Hess2021/10/01 09:40 AM
                                  MMU privilegessr2021/09/21 10:07 AM
                                    MMU privilegesLinus Torvalds2021/09/21 12:49 PM
                            Virtually tagged L1-cachesKonrad Schwarz2021/09/16 03:18 AM
                          Virtually tagged L1-cachesCarson2021/09/16 12:12 PM
                            Virtually tagged L1-cachesanon22021/09/16 04:16 PM
                              Virtually tagged L1-cachesrwessel2021/09/16 05:29 PM
                          Virtually tagged L1-cachessr2021/09/20 03:20 AM
              Virtually tagged L1-caches---2021/09/08 01:28 PM
                Virtually tagged L1-cachesanonymou52021/09/08 07:28 PM
                  Virtually tagged L1-cachesanonymou52021/09/08 07:34 PM
                  Virtually tagged L1-caches---2021/09/09 09:14 AM
                    Virtually tagged L1-cachesanonymou52021/09/09 09:44 PM
                Multi-threading?David Kanter2021/09/09 08:32 PM
                  Multi-threading?---2021/09/10 08:19 AM
                Virtually tagged L1-cachessr2021/09/11 12:19 AM
                Virtually tagged L1-cachessr2021/09/11 12:36 AM
                  Virtually tagged L1-caches---2021/09/11 08:53 AM
                    Virtually tagged L1-cachessr2021/09/11 11:43 PM
                      Virtually tagged L1-cachesLinus Torvalds2021/09/12 10:10 AM
                        Virtually tagged L1-cachessr2021/09/12 10:57 AM
                          Virtually tagged L1-cachesdmcq2021/09/13 07:31 AM
                            Virtually tagged L1-cachessr2021/09/20 03:11 AM
            Virtually tagged L1-cachessr2021/09/11 01:49 AM
      Virtually tagged L1-cachesLinus Torvalds2021/09/08 11:34 AM
        Virtually tagged L1-cachesdmcq2021/09/09 01:46 AM
          Virtually tagged L1-cachesdmcq2021/09/09 01:58 AM
          Virtually tagged L1-cachessr2021/09/11 12:29 AM
            Virtually tagged L1-cachesdmcq2021/09/11 07:59 AM
              Virtually tagged L1-cachessr2021/09/11 11:57 PM
                Virtually tagged L1-cachesdmcq2021/09/12 07:44 AM
                  Virtually tagged L1-cachessr2021/09/12 08:48 AM
                    Virtually tagged L1-cachesdmcq2021/09/12 12:22 PM
                      Virtually tagged L1-cachessr2021/09/20 03:40 AM
    Where do you see this information? (NT)anon22021/09/09 01:45 AM
      Where do you see this information?sr2021/09/11 12:40 AM
        Where do you see this information?anon22021/09/11 12:53 AM
          Where do you see this information?sr2021/09/11 01:08 AM
            Thank you (NT)anon22021/09/11 03:31 PM
Reply to this Topic
Body: No Text
How do you spell avocado?