Re: Why does the location of PAD move around?

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From	Paul Rubin <no.email@nospam.invalid>
Newsgroups	comp.lang.forth
Subject	Re: Why does the location of PAD move around?
Date	Sun, 02 Apr 2017 22:04:13 -0700
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albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) writes:
> The following 4 screens taken from ciforth contain both...
> This code is tricky. 

Thanks!  I'll try to figure it out.

For preemptive the central point is the

> For the cooperative code keep in mind that in ciforth the only
> pseudoregister to switch is the return stack. The data stack pointer
> was stored on the return stack and the user variables are
> coupled to the return stack pointer. The interpreter pointer
> is incremented as usual, executing code even if that code
> is switching to another task.

I don't understand the part about the user variables being compled to
the return stack pointer, but I think the rest is pretty standard
(e.g. pushing the other registers on the return stack so only the task
RP has to be stored in the TCB).  I'm surprised about being expected to
have an 84-byte PAD for each task though I guess if memory is short, the
magic words "environmental dependency" can make PAD smaller.

Thread

Why does the location of PAD move around? Rod Pemberton <NeedNotReplyHere@xrsevnneqk.cem> - 2017-04-01 21:07 -0400
  Re: Why does the location of PAD move around? hughaguilar96@gmail.com - 2017-04-01 19:32 -0700
    Re: Why does the location of PAD move around? Rod Pemberton <NeedNotReplyHere@xrsevnneqk.cem> - 2017-04-02 02:00 -0400
      Re: Why does the location of PAD move around? Julian Fondren <julian.fondren@gmail.com> - 2017-04-01 23:51 -0700
        Re: Why does the location of PAD move around? "Elizabeth D. Rather" <erather@forth.com> - 2017-04-01 21:59 -1000
        Re: Why does the location of PAD move around? krishna.myneni@ccreweb.org - 2017-04-09 09:54 -0700
  Re: Why does the location of PAD move around? Julian Fondren <julian.fondren@gmail.com> - 2017-04-01 20:10 -0700
    Re: Why does the location of PAD move around? "Elizabeth D. Rather" <erather@forth.com> - 2017-04-01 18:39 -1000
    Re: Why does the location of PAD move around? Mark Wills <markwills1970@gmail.com> - 2017-04-02 08:29 -0700
  Re: Why does the location of PAD move around? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-02 04:13 -0500
    Re: Why does the location of PAD move around? Paul Rubin <no.email@nospam.invalid> - 2017-04-02 18:08 -0700
      Re: Why does the location of PAD move around? Julian Fondren <julian.fondren@gmail.com> - 2017-04-02 18:13 -0700
        Re: Why does the location of PAD move around? Paul Rubin <no.email@nospam.invalid> - 2017-04-02 18:22 -0700
          Re: Why does the location of PAD move around? Julian Fondren <julian.fondren@gmail.com> - 2017-04-02 18:31 -0700
          Re: Why does the location of PAD move around? albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-03 04:37 +0200
            Re: Why does the location of PAD move around? Paul Rubin <no.email@nospam.invalid> - 2017-04-02 22:04 -0700
              Re: Why does the location of PAD move around? albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-04 13:47 +0200
                Re: Why does the location of PAD move around? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-04 10:53 -0500
                Re: Why does the location of PAD move around? Alex <alex@rivadpm.com> - 2017-04-04 17:04 +0100
                Re: Why does the location of PAD move around? albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-04 19:00 +0200
                Re: Why does the location of PAD move around? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-05 03:39 -0500
                Re: Why does the location of PAD move around? Alex <alex@rivadpm.com> - 2017-04-05 19:17 +0100
            Re: Why does the location of PAD move around? "Elizabeth D. Rather" <erather@forth.com> - 2017-04-02 21:44 -1000
          Re: Why does the location of PAD move around? "Elizabeth D. Rather" <erather@forth.com> - 2017-04-02 21:35 -1000
          Re: Why does the location of PAD move around? Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-03 03:38 -0500
          Re: Why does the location of PAD move around? "HAA" <someone@microsoft.com> - 2017-04-05 11:25 +1000
            Re: Why does the location of PAD move around? Paul Rubin <no.email@nospam.invalid> - 2017-04-05 18:23 -0700
              Re: Why does the location of PAD move around? "HAA" <someone@microsoft.com> - 2017-04-07 14:26 +1000
                Re: Why does the location of PAD move around? Alex <alex@rivadpm.com> - 2017-04-07 08:47 +0100
                Re: Why does the location of PAD move around? "HAA" <someone@microsoft.com> - 2017-04-08 10:25 +1000
                Re: Why does the location of PAD move around? Paul Rubin <no.email@nospam.invalid> - 2017-04-07 20:37 -0700
                Re: Why does the location of PAD move around? Alex <alex@rivadpm.com> - 2017-04-08 12:42 +0100
                Re: Why does the location of PAD move around? jason.songhurst@gmail.com - 2017-04-08 20:28 -0700
                Re: Why does the location of PAD move around? Coos Haak <htrofhc@gmail.com> - 2017-04-09 13:47 +0200
                Re: Why does the location of PAD move around? "Elizabeth D. Rather" <erather@forth.com> - 2017-04-09 08:36 -1000
                Re: Why does the location of PAD move around? albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-09 14:48 +0200
                Re: Why does the location of PAD move around? "HAA" <someone@microsoft.com> - 2017-04-10 10:31 +1000
                Re: Why does the location of PAD move around? Alex <alex@rivadpm.com> - 2017-04-10 09:29 +0100
                Re: Why does the location of PAD move around? albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-10 11:57 +0200
      Re: Why does the location of PAD move around? albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-03 03:43 +0200
        Re: Why does the location of PAD move around? "Elizabeth D. Rather" <erather@forth.com> - 2017-04-02 21:53 -1000
  Re: Why does the location of PAD move around? "HAA" <someone@microsoft.com> - 2017-04-02 21:31 +1000
    Re: Why does the location of PAD move around? Coos Haak <htrofhc@gmail.com> - 2017-04-02 15:12 +0200
      Re: Why does the location of PAD move around? "HAA" <someone@microsoft.com> - 2017-04-03 10:46 +1000
        Re: Why does the location of PAD move around? albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-03 03:31 +0200
          Re: Why does the location of PAD move around? hughaguilar96@gmail.com - 2017-04-02 19:14 -0700
        Re: Why does the location of PAD move around? "Elizabeth D. Rather" <erather@forth.com> - 2017-04-02 21:55 -1000
          Re: Why does the location of PAD move around? "HAA" <someone@microsoft.com> - 2017-04-04 11:06 +1000
            Re: Why does the location of PAD move around? Alex <alex@rivadpm.com> - 2017-04-04 12:54 +0100
              Re: Why does the location of PAD move around? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-04 16:27 +0000
                Re: Why does the location of PAD move around? Alex <alex@rivadpm.com> - 2017-04-04 19:23 +0100
          Re: Why does the location of PAD move around? hughaguilar96@gmail.com - 2017-04-07 22:04 -0700
    Re: Why does the location of PAD move around? hughaguilar96@gmail.com - 2017-04-02 14:21 -0700
  Why does the location of PAD move around? Mark Wills <markwills1970@gmail.com> - 2017-04-02 08:28 -0700
    Re: Why does the location of PAD move around? hughaguilar96@gmail.com - 2017-04-02 13:47 -0700
      Re: Why does the location of PAD move around? hughaguilar96@gmail.com - 2017-04-02 15:13 -0700
        Re: Why does the location of PAD move around? hughaguilar96@gmail.com - 2017-04-02 18:55 -0700

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