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Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's 41 Floppies Worth

From	Johnny Billquist <bqt@softjar.se>
Newsgroups	comp.os.linux.misc, alt.folklore.computers
Subject	Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's 41 Floppies Worth
Date	2025-08-29 21:12 +0200
Organization	MGT Consulting
Message-ID	<108su32$3e8$1@news.misty.com> (permalink)
References	<e4ucnb1I-5IIqur1nZ2dnZfqnPudnZ2d@giganews.com> <105fgk4$2ka5f$1@dont-email.me> <20250721093237.0000674f@gmail.com> <108k7rn$e12$4@news.misty.com> <108l4vk$77t$1@gal.iecc.com>

Cross-posted to 2 groups.

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On 2025-08-26 22:21, John Levine wrote:
> According to Johnny Billquist  <bqt@softjar.se>:
>> The claim has another problem. While an x86 might be considered more
>> powerful in some ways, it does not have nearly as capably MMU as the
>> PDP-11,
> 
> The 8086 had no MMU at all, but small model code gave you 64K each of
> instructions and data, the same as what the 11's MMU gave you. There was no
> hardware protection so a malicious or badly broken program could crash the
> system but they rarely did. That would require instructions that the C compiler
> didn't generate.

If we were to compare the memory layout/concepts of the PDP-11 and x86, 
with an eye to powerful and capable, then the PDP-11, which have an MMU, 
don't need to allocate 64K of memory for each process. In fact, it only 
need to allocate as much memory as the process actually require, and any 
addressing outside of that would trap and you'd get an signal in your 
process. So you can easily squish in many more processes in the same 
amount of memory.
The next couple of points I don't know exactly when they came about for 
the PDP-11, so it might have been a bit later, but I think it's still 
valid as a comparison against the x86 here.
Stack, on the PDP-11 is dynamically grown and allocated while the 
program is running, so you don't have to pre-allocate all that memory 
either, even though it can grow up to close to 64K.

But even more important, on the PDP-11, there is support for overlaid 
programs, which makes heavy use of the MMU. Basically, programs can be 
way larger than 64K code. You can place functions in different overlays, 
and call between them, and you can run up to many hundred of K of code 
very easy and straight forward on the PDP-11, and it's all because the 
MMU helps you out with it, moving the pages mapping around as needed.

> I worked on PC/IX which was a straightforward port of PDP-11 System III Unix to
> the PC. It wasn't particularly fast, but all the C programs that ran on the 11
> also ran on PC/IX. It was quite reliable. I recall that we got a bug report
> about something that only broke if the system had been up continuously for a
> year.

And the PDP-11 grew more capable in ways the PC/IX would not be able to 
follow, getting programs you would not have been able to run on that PC.

   Johnny

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Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Johnny Billquist <bqt@softjar.se> - 2025-08-26 14:04 +0200
  Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth The Natural Philosopher <tnp@invalid.invalid> - 2025-08-26 13:13 +0100
    Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Johnny Billquist <bqt@softjar.se> - 2025-08-26 15:23 +0200
      Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth The Natural Philosopher <tnp@invalid.invalid> - 2025-08-26 19:43 +0100
  Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth John Ames <commodorejohn@gmail.com> - 2025-08-26 08:31 -0700
    Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth "Kerr-Mudd, John" <admin@127.0.0.1> - 2025-08-26 17:52 +0100
      Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth John Ames <commodorejohn@gmail.com> - 2025-08-26 10:01 -0700
      Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth The Natural Philosopher <tnp@invalid.invalid> - 2025-08-26 19:44 +0100
    Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Rich <rich@example.invalid> - 2025-08-26 17:26 +0000
      Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth ted@loft.tnolan.com (Ted Nolan <tednolan>) - 2025-08-26 17:47 +0000
        Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth scott@slp53.sl.home (Scott Lurndal) - 2025-08-26 18:19 +0000
        Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth John Levine <johnl@taugh.com> - 2025-08-26 20:25 +0000
          Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth The Natural Philosopher <tnp@invalid.invalid> - 2025-08-26 21:44 +0100
          Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth ted@loft.tnolan.com (Ted Nolan <tednolan>) - 2025-08-26 21:12 +0000
    Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth antispam@fricas.org (Waldek Hebisch) - 2025-08-27 22:09 +0000
      Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-08-27 23:00 +0000
        Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth antispam@fricas.org (Waldek Hebisch) - 2025-08-28 09:10 +0000
        Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth "Carlos E.R." <robin_listas@es.invalid> - 2025-08-28 13:02 +0200
          Re: Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth The Natural Philosopher <tnp@invalid.invalid> - 2025-08-28 12:17 +0100
  Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth John Levine <johnl@taugh.com> - 2025-08-26 20:21 +0000
    Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Alexander Schreiber <als@usenet.thangorodrim.de> - 2025-08-27 16:40 +0200
      Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth John Ames <commodorejohn@gmail.com> - 2025-08-27 08:30 -0700
        Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Alexander Schreiber <als@usenet.thangorodrim.de> - 2025-08-28 10:09 +0200
      Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth "Kerr-Mudd, John" <admin@127.0.0.1> - 2025-08-27 19:04 +0100
        Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-08-27 22:58 +0000
        Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth c186282 <c186282@nnada.net> - 2025-08-28 04:06 -0400
      Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-08-27 22:58 +0000
      Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth c186282 <c186282@nnada.net> - 2025-08-28 03:26 -0400
        Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Peter Flass <Peter@Iron-Spring.com> - 2025-08-28 15:56 -0700
          Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-08-29 00:58 +0000
      Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2025-08-29 06:50 +0000
        Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth The Natural Philosopher <tnp@invalid.invalid> - 2025-08-29 10:50 +0100
          Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Rich <rich@example.invalid> - 2025-08-31 20:15 +0000
        Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Alexander Schreiber <als@usenet.thangorodrim.de> - 2025-08-29 12:46 +0200
          Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Richard Kettlewell <invalid@invalid.invalid> - 2025-08-29 14:28 +0100
          Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Bob Eager <news0009@eager.cx> - 2025-08-29 14:40 +0000
            Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Alexander Schreiber <als@usenet.thangorodrim.de> - 2025-08-29 23:13 +0200
              Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-08-30 03:28 +0000
          Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2025-08-29 23:51 +0000
            Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-08-30 03:27 +0000
              Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth c186282 <c186282@nnada.net> - 2025-08-30 00:25 -0400
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth cross@spitfire.i.gajendra.net (Dan Cross) - 2025-08-30 12:19 +0000
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth "Carlos E.R." <robin_listas@es.invalid> - 2025-08-31 13:37 +0200
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Alexander Schreiber <als@usenet.thangorodrim.de> - 2025-08-31 18:23 +0200
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth rbowman <bowman@montana.com> - 2025-08-31 17:37 +0000
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-08-31 22:24 +0000
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth "Carlos E.R." <robin_listas@es.invalid> - 2025-09-01 02:35 +0200
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Peter Flass <Peter@Iron-Spring.com> - 2025-09-01 07:55 -0700
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Rich <rich@example.invalid> - 2025-09-01 11:23 +0000
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth antispam@fricas.org (Waldek Hebisch) - 2025-09-01 11:52 +0000
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth "Carlos E.R." <robin_listas@es.invalid> - 2025-09-01 14:11 +0200
              Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth candycanearter07 <candycanearter07@candycanearter07.nomail.afraid> - 2025-08-30 18:30 +0000
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-08-30 22:20 +0000
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Alexander Schreiber <als@usenet.thangorodrim.de> - 2025-08-31 18:25 +0200
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2025-09-02 21:22 +0000
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth scott@slp53.sl.home (Scott Lurndal) - 2025-09-02 21:46 +0000
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-09-02 22:44 +0000
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2025-09-02 23:55 +0000
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Johnny Billquist <bqt@softjar.se> - 2025-09-03 01:22 +0200
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth antispam@fricas.org (Waldek Hebisch) - 2025-09-03 01:13 +0000
            Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Rich <rich@example.invalid> - 2025-08-31 20:20 +0000
            Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Anssi Saari <anssi.saari@usenet.mail.kapsi.fi> - 2025-09-01 14:46 +0300
              Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth scott@slp53.sl.home (Scott Lurndal) - 2025-09-01 14:33 +0000
              Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Peter Flass <Peter@Iron-Spring.com> - 2025-09-01 08:03 -0700
        Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth "Carlos E.R." <robin_listas@es.invalid> - 2025-08-29 14:53 +0200
        Re: PC/IX, Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth John Levine <johnl@taugh.com> - 2025-08-29 17:09 +0000
          Re: PC/IX, Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth The Natural Philosopher <tnp@invalid.invalid> - 2025-08-29 19:18 +0100
            Re: PC/IX, Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2025-08-29 23:51 +0000
              Re: PC/IX, Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth rbowman <bowman@montana.com> - 2025-08-30 05:54 +0000
                Re: PC/IX, Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth c186282 <c186282@nnada.net> - 2025-08-30 03:06 -0400
                Re: PC/IX, Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth The Natural Philosopher <tnp@invalid.invalid> - 2025-08-30 08:28 +0100
                Re: PC/IX, Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth c186282 <c186282@nnada.net> - 2025-08-30 05:30 -0400
                Re: PC/IX, Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth The Natural Philosopher <tnp@invalid.invalid> - 2025-08-30 11:59 +0100
                Re: PC/IX, Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth c186282 <c186282@nnada.net> - 2025-08-30 08:26 -0400
                Re: PC/IX, Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth rbowman <bowman@montana.com> - 2025-08-30 20:36 +0000
                Re: PC/IX, Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth rbowman <bowman@montana.com> - 2025-08-30 20:31 +0000
                Re: PC/IX, Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2025-09-02 21:22 +0000
                Re: PC/IX, Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth rbowman <bowman@montana.com> - 2025-09-03 03:10 +0000
              Re: PC/IX, Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth The Natural Philosopher <tnp@invalid.invalid> - 2025-08-30 08:13 +0100
        Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth scott@slp53.sl.home (Scott Lurndal) - 2025-08-29 22:27 +0000
    Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Johnny Billquist <bqt@softjar.se> - 2025-08-29 21:12 +0200
      Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth ted@loft.tnolan.com (Ted Nolan <tednolan>) - 2025-08-29 20:52 +0000
        Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-08-29 23:34 +0000
          Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Johnny Billquist <bqt@softjar.se> - 2025-08-30 11:51 +0200
          Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth scott@slp53.sl.home (Scott Lurndal) - 2025-08-30 15:54 +0000
            Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Peter Flass <Peter@Iron-Spring.com> - 2025-08-30 12:13 -0700
              Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth ted@loft.tnolan.com (Ted Nolan <tednolan>) - 2025-08-30 19:27 +0000
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Peter Flass <Peter@Iron-Spring.com> - 2025-08-30 14:45 -0700
              Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2025-09-02 21:22 +0000
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth John Ames <commodorejohn@gmail.com> - 2025-09-02 14:45 -0700
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth scott@slp53.sl.home (Scott Lurndal) - 2025-09-02 22:03 +0000
            Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Rich Alderson <news@alderson.users.panix.com> - 2025-08-30 19:34 -0400
          Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth "Carlos E.R." <robin_listas@es.invalid> - 2025-08-31 13:44 +0200
            Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-09-01 02:36 +0000
              Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth c186282 <c186282@nnada.net> - 2025-09-01 01:52 -0400
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth "Carlos E.R." <robin_listas@es.invalid> - 2025-09-01 11:26 +0200
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Peter Flass <Peter@Iron-Spring.com> - 2025-09-01 08:01 -0700
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth rbowman <bowman@montana.com> - 2025-09-01 18:12 +0000
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth "Carlos E.R." <robin_listas@es.invalid> - 2025-09-01 20:15 +0200
              Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth "Carlos E.R." <robin_listas@es.invalid> - 2025-09-01 11:20 +0200
        Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Johnny Billquist <bqt@softjar.se> - 2025-08-30 11:49 +0200
          Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth ted@loft.tnolan.com (Ted Nolan <tednolan>) - 2025-08-30 17:39 +0000
            Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Johnny Billquist <bqt@softjar.se> - 2025-08-31 12:40 +0200
              Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Peter Flass <Peter@Iron-Spring.com> - 2025-08-31 08:19 -0700
                Re: Unix on x86, Hmmm ... Downloaded Xenix - But It's *41* Floppies Worth Johnny Billquist <bqt@softjar.se> - 2025-08-31 20:10 +0200

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