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Re: Apollo 11 source code released

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On 16-07-12 21:41 , JF Mezei wrote:
> On 2016-07-11 20:58, Jeff Findley wrote:
>
>> Could linkers of the time recognize duplicate functions (different name,
>> but functionally identical) and discard the duplicate when linking?
>
> No. and I doubt that current linkers do.  They will detect duplicate
> function definitions.

Here is the reference I found after Jeff's post, from 2005: 
http://blog.vladimirprus.com/2005/03/duplicate-function-bodies.html

Quote: "A couple of days ago I've learned that the Microsoft linker can 
merge functions with binary identical bodies." Link: 
https://blogs.msdn.microsoft.com/oldnewthing/20050322-00/?p=36113/

> Where early linkers did work no longer necessary is workout overlays.

That linker feature is still used in some small systems where the 
architecture limits the address size but applications need more memory, 
so the memory is "paged" or "mapped" or "banked" dynamically. Say, the 
architectural address is 16 bits but there is 1 MiB of memory (RAM, not 
disk) with a 20-bit physical address. The processor then provides 4 
"extension" or "mapping" bits that can be set to view different parts of 
the memory through the 16-bit, 64 KiB windows. Well, usually the low end 
of the memory address is not mapped, so that some core code is visible 
in all mappings.

Many current Intel-8051 microcontrollers (8-bit or 16-bit architectural 
address) use this kind of memory "overlay". Atmel's 8-bit AVR 
architecture also has such features, IIRC.

On the Modcomp IV minicomputer this was actually called "virtual memory" 
and used as such: each program/process had a 16-bit "virtual" address 
space but several programs/processes could be loaded at once into the 
larger physical memory.

> When you have limited memory, different subroutines/modules would be
> linked with the same memory addresses. But only one would be loaded at a
> time, and on sime systems this unloading of one module and loading of
> next was automatic (and slow). *(think of it as poor man's virtual memory).

In the paged/mapped "overlay" systems, "loading" an overlay just means 
changing the address-extension/mapping bits, so its very fast. (But some 
linkers can/could be very slow at finding a workable overlay structure 
automatically. I remember an HP brochure for the HP21MX computers, with 
a 16-bit basic address but up to 2 MiB of memory. It quoted linking 
times of some number of hours for large, but less than 2 MiB, overlaid 
applications).

The Wikipedia entry on the AGC mentions three registers which seem to be 
a kind of memory-address-extension register: Bank/Fbank, Ebank, and Sbank.

> In various Apollo themed movies/TV series, you often hear about "loading
> program 64" and this is likely what happened.

The AGC had no "mass memory" -- drum or disk -- only the core memory, 
which was directly addressable, no "loading" needed. From where would a 
program be loaded? This is just a guess, but to me it seems more likely 
that "loading a program" meant starting the program and/or bringing it 
into "focus" for commands, inputs, and outputs.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .

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Apollo 11 source code released JF Mezei <jfmezei.spamnot@vaxination.ca> - 2016-07-10 12:43 -0400
  Re: Apollo 11 source code released Niklas Holsti <niklas.holsti@tidorum.invalid> - 2016-07-10 20:33 +0300
    Re: Apollo 11 source code released JF Mezei <jfmezei.spamnot@vaxination.ca> - 2016-07-10 18:28 -0400
      Re: Apollo 11 source code released Jeff Findley <jfindley@cinci.nospam.rr.com> - 2016-07-10 21:27 -0400
      Re: Apollo 11 source code released Fred J. McCall <fjmccall@gmail.com> - 2016-07-11 00:36 -0700
        Re: Apollo 11 source code released Jeff Findley <jfindley@cinci.nospam.rr.com> - 2016-07-11 06:44 -0400
          Re: Apollo 11 source code released Niklas Holsti <niklas.holsti@tidorum.invalid> - 2016-07-11 16:20 +0300
            Re: Apollo 11 source code released Jeff Findley <jfindley@cinci.nospam.rr.com> - 2016-07-11 20:53 -0400
              Re: Apollo 11 source code released JF Mezei <jfmezei.spamnot@vaxination.ca> - 2016-07-12 14:36 -0400
                Re: Apollo 11 source code released Fred J. McCall <fjmccall@gmail.com> - 2016-07-12 18:11 -0700
              Re: Apollo 11 source code released Niklas Holsti <niklas.holsti@tidorum.invalid> - 2016-07-12 23:37 +0300
                Re: Apollo 11 source code released Fred J. McCall <fjmccall@gmail.com> - 2016-07-12 18:14 -0700
                Re: Apollo 11 source code released Niklas Holsti <niklas.holsti@tidorum.invalid> - 2016-07-13 21:01 +0300
                Re: Apollo 11 source code released Fred J. McCall <fjmccall@gmail.com> - 2016-07-13 20:06 -0700
                Re: Apollo 11 source code released Jeff Findley <jfindley@cinci.nospam.rr.com> - 2016-07-14 06:44 -0400
                Re: Apollo 11 source code released Niklas Holsti <niklas.holsti@tidorum.invalid> - 2016-07-15 23:54 +0300
                Re: Apollo 11 source code released JF Mezei <jfmezei.spamnot@vaxination.ca> - 2016-07-17 11:49 -0400
                Re: Apollo 11 source code released William Mook <mokmedical@gmail.com> - 2016-07-17 18:41 -0700
                Re: Apollo 11 source code released Niklas Holsti <niklas.holsti@tidorum.invalid> - 2016-07-18 09:20 +0300
                Re: Apollo 11 source code released JF Mezei <jfmezei.spamnot@vaxination.ca> - 2016-07-14 11:38 -0400
                Re: Apollo 11 source code released Niklas Holsti <niklas.holsti@tidorum.invalid> - 2016-07-16 00:10 +0300
                Re: Apollo 11 source code released Niklas Holsti <niklas.holsti@tidorum.invalid> - 2016-07-15 22:26 +0300
                Re: Apollo 11 source code released Fred J. McCall <fjmccall@gmail.com> - 2016-07-20 10:49 -0700
              Re: Apollo 11 source code released Snidely <snidely.too@gmail.com> - 2016-07-14 09:12 -0700
          Re: Apollo 11 source code released JF Mezei <jfmezei.spamnot@vaxination.ca> - 2016-07-11 11:51 -0400
            Re: Apollo 11 source code released Niklas Holsti <niklas.holsti@tidorum.invalid> - 2016-07-12 02:19 +0300
              Re: Apollo 11 source code released Jeff Findley <jfindley@cinci.nospam.rr.com> - 2016-07-11 20:58 -0400
                Re: Apollo 11 source code released Niklas Holsti <niklas.holsti@tidorum.invalid> - 2016-07-12 09:24 +0300
                Re: Apollo 11 source code released Fred J. McCall <fjmccall@gmail.com> - 2016-07-12 10:10 -0700
                Re: Apollo 11 source code released Niklas Holsti <niklas.holsti@tidorum.invalid> - 2016-07-13 21:07 +0300
                Re: Apollo 11 source code released Fred J. McCall <fjmccall@gmail.com> - 2016-07-13 20:08 -0700
                Re: Apollo 11 source code released JF Mezei <jfmezei.spamnot@vaxination.ca> - 2016-07-14 11:25 -0400
                Re: Apollo 11 source code released Niklas Holsti <niklas.holsti@tidorum.invalid> - 2016-07-15 22:39 +0300
                Re: Apollo 11 source code released Fred J. McCall <fjmccall@gmail.com> - 2016-07-20 10:40 -0700
                Re: Apollo 11 source code released JF Mezei <jfmezei.spamnot@vaxination.ca> - 2016-07-12 14:41 -0400
                Re: Apollo 11 source code released Niklas Holsti <niklas.holsti@tidorum.invalid> - 2016-07-12 23:26 +0300
                Re: Apollo 11 source code released Jeff Findley <jfindley@cinci.nospam.rr.com> - 2016-07-12 21:41 -0400
                Re: Apollo 11 source code released Niklas Holsti <niklas.holsti@tidorum.invalid> - 2016-07-13 08:54 +0300
                Re: Apollo 11 source code released Jeff Findley <jfindley@cinci.nospam.rr.com> - 2016-07-13 06:43 -0400
                Re: Apollo 11 source code released Niklas Holsti <niklas.holsti@tidorum.invalid> - 2016-07-13 21:08 +0300
                Re: Apollo 11 source code released JF Mezei <jfmezei.spamnot@vaxination.ca> - 2016-07-14 11:34 -0400
                Re: Apollo 11 source code released Niklas Holsti <niklas.holsti@tidorum.invalid> - 2016-07-15 23:06 +0300
                Re: Apollo 11 source code released Jeff Findley <jfindley@cinci.nospam.rr.com> - 2016-07-15 19:48 -0400
                Re: Apollo 11 source code released Jeff Findley <jfindley@cinci.nospam.rr.com> - 2016-07-15 19:59 -0400
                Re: Apollo 11 source code released JF Mezei <jfmezei.spamnot@vaxination.ca> - 2016-07-17 12:00 -0400
                Re: Apollo 11 source code released Jeff Findley <jfindley@cinci.nospam.rr.com> - 2016-07-17 12:14 -0400
                Re: Apollo 11 source code released JF Mezei <jfmezei.spamnot@vaxination.ca> - 2016-07-17 12:56 -0400
              Re: Apollo 11 source code released Fred J. McCall <fjmccall@gmail.com> - 2016-07-12 10:04 -0700
            Re: Apollo 11 source code released Fred J. McCall <fjmccall@gmail.com> - 2016-07-12 09:43 -0700
          Re: Apollo 11 source code released Alain Fournier <alain245@videotron.ca> - 2016-07-11 19:43 -0400
  Re: Apollo 11 source code released Fred J. McCall <fjmccall@gmail.com> - 2016-07-10 11:39 -0700
  Re: Apollo 11 source code released William Mook <mokmedical@gmail.com> - 2016-07-11 18:28 -0700

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