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Open source CPU+open source toolchain

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  Open source CPU+open source toolchain foxaudioresearch@gmail.com - 2015-07-29 17:57 -0700
    Re: Open source CPU+open source toolchain mentificium@gmail.com - 2015-07-29 18:36 -0700
      Re: Open source CPU+open source toolchain foxaudioresearch@gmail.com - 2015-07-29 19:15 -0700
    Re: Open source CPU+open source toolchain rickman <gnuarm@gmail.com> - 2015-07-30 01:40 -0400
      Re: Open source CPU+open source toolchain foxaudioresearch@gmail.com - 2015-07-30 07:11 -0700
      Re: Open source CPU+open source toolchain Jecel <jecel@merlintec.com> - 2015-07-30 09:39 -0700
      Re: Open source CPU+open source toolchain "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-07-30 21:22 -0400
        Re: Open source CPU+open source toolchain "Elizabeth D. Rather" <erather@forth.com> - 2015-07-30 20:56 -0500
          Re: Open source CPU+open source toolchain "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-07-30 22:05 -0400
            Re: Open source CPU+open source toolchain "Elizabeth D. Rather" <erather@forth.com> - 2015-07-31 09:47 -0500
              Re: Open source CPU+open source toolchain "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-07-31 23:57 -0400
                Re: Open source CPU+open source toolchain anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-08-01 13:07 +0000
                Re: Open source CPU+open source toolchain "Elizabeth D. Rather" <erather@forth.com> - 2015-08-01 10:37 -0500
    Re: Open source CPU+open source toolchain mfanyikazi@gmail.com - 2015-08-02 01:46 -0700
      Re: Open source CPU+open source toolchain foxaudioresearch@gmail.com - 2015-08-02 07:55 -0700
        Re: Open source CPU+open source toolchain rickman <gnuarm@gmail.com> - 2015-08-02 12:06 -0400
          Re: Open source CPU+open source toolchain foxaudioresearch@gmail.com - 2015-08-04 08:10 -0700
            Re: Open source CPU+open source toolchain rickman <gnuarm@gmail.com> - 2015-08-04 12:05 -0400
              Re: Open source CPU+open source toolchain foxaudioresearch@gmail.com - 2015-08-04 14:21 -0700
                Re: Open source CPU+open source toolchain rickman <gnuarm@gmail.com> - 2015-08-04 18:24 -0400
        Re: Open source CPU+open source toolchain Jan Coombs <Jan-54 <jenfhaomndgfwutc@murmic.plus.com>> - 2015-08-06 09:12 +0100

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#41142

On Sun, 2 Aug 2015 07:55:52 -0700 (PDT)
foxaudioresearch@gmail.com wrote:

> I read some things about multi-tasking and the J1. It is a
> thorny problem however is not the correct solution to add some
> support at the CPU level?  
> 
> Something like bigger stacks that could be segmented by task
> comes to mind. I think the stack rollover is a possible threat
> but hey Forth people know how to keep the stack under control
> (at least in finished code) :)
> 
> Koopman indicates that you can run real Forth programs with 16
> cells per stack.
> 
> Would that solve the multi-tasking problem for a specific
> maximum number of tasks?  (ie we would not be running UNIX on
> the thing, just some embedded programs)

Yes, the hardware additions are practical and not complex.   

In the (iCE40) chips used the RAM blocks used for stacks are
likely 256x16b per stack, so there is a lot of unused space.
This could be partitioned to support stacks for 2-16 tasks.

Adding special RAM mapping for user variable would be a little
more complex. 

Task selection could be controlled by a register mapped into I/O
space. Alternatively it could be incorporated in the j1
instruction set.  The unused bit in the instruction word could
be used to change the operation of the four bit stack pointer
control field to set the task number. 

Jan Coombs
-- 
email valid, else fix dots and hyphen
jan4clf2014@murrayhyphenmicroftdotcodotuk

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