Re: Forth Implementations advantages and disadvantages.

From	Cecil Bayona <cbayona@cbayona.com>
Newsgroups	comp.lang.forth
Subject	Re: Forth Implementations advantages and disadvantages.
Date	2017-06-01 11:27 -0500
Organization	A noiseless patient Spider
Message-ID	<ogpf3i$ea6$1@dont-email.me> (permalink)
References	(5 earlier) <ogdg19$6tj$1@dont-email.me> <76d52560-abac-4a83-a208-f63355f8852e@googlegroups.com> <ogetaf$3jc$1@dont-email.me> <f29ebb3b-e12c-4338-81ec-0039204ad3e3@googlegroups.com> <930cc033-885e-4a45-945e-f202af41f0b5@googlegroups.com>

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On 5/28/2017 8:25 PM, hughaguilar96@gmail.com wrote:
> On Sunday, May 28, 2017 at 2:45:19 PM UTC-7, hughag...@gmail.com wrote:
>> On Sunday, May 28, 2017 at 9:22:57 AM UTC-7, Cecil - k5nwa wrote:
>>> On 5/28/2017 12:10 AM, hughaguilar96@gmail.com wrote:
>>>> I just came up with this for a PDP11 STC off the top of my head, but it seems like it might work:
>>>>
>>>> R0 general-purpose
>>>> R1 general-purpose
>>>> R2 top-of-stack
>>>> R3 local-frame pointer
>>>> R4 data-stack pointer
>>>> R5 double-stack pointer
>>>> R6 return-stack pointer
>>>> R7 program counter
>>> ...
>>> Thanks for reminding me about PAC (Portable Assembler Code), it changes
>>> the whole trajectory of the project, if PAC  can generate efficient code
>>> then it would be an ideal setup for this and other projects. In any case
>>> it is bound to be faster than using C.
>> ...
>> The MSP430 has 16 registers total. I would still use the PDP11 as your assembly-language as I described above. You can, however, have the main-program use some of the registers, and ISRs use the other registers. This means that ISRs don't have to save and restore registers (assuming that ISRs can't be interrupted). This should boost the speed of your system considerably, as a lot of micro-controller programs spend up to 50% of their time servicing interrupts. You will have to write your compiler in such a way that it is able to use the correct set of registers as R0..R7 depending upon whether it is compiling a colon word to be used in the main-program or is compiling an ISR. This should be easy. Put the functions that can be used by the main-program in one vocabulary and the functions that can be used by ISRs in another vocabulary, so there is no confusion if they have the same names.
> 
> The more that I think about it, the more I like the PDP11 as your portable-assembly-language.
> 
> 1.) The 8 registers of the PDP11 are adequate for a reasonable Forth implementation (as shown above in the register-dedication table I provided). You do have two general-purpose registers, so you can do code-optimization in which you hold values in general-purpose registers temporarily rather than push them to the data-stack (VFX does code optimization on the 32-bit x86 that has only one more register than the PDP11 has).
> 
> 2.) On modern processors that have 16 registers (such as the MSP430), you can divide the registers into two banks for the main-program and the ISRs to significantly speed up ISRs while still allowing ISRs to be written in Forth. Your ISRs can't be interrupted though, because there is only one bank of registers available. On the PIC24 you can also have fast ISRs written in assembly-language that only use the lower four registers and are able to interrupt the lower-priority ISRs that are written in Forth.
> 
> 3.) There are HDL implementations of the PDP11 already available, so if you want an FPGA you can use one of these as a starting point. Considering that you (and I) have little or no experience with HDL, it seems more realistic to start with an existing implementation rather than start from scratch.
> 
> 4.) There is software available for the PDP11, such as RT11, that could still be useful. Your assembler should be compatible with whatever assembler was used to assemble the RT11 code, except that your assembler generates code for the MSP430, PIC24, etc.. So, if the source-code to RT11 is available (I assume it is), you could run RT11 on an MSP430 or PIC24 or whatever. It will be just like a George Romero movie: the dead will rise and walk again!
> 

I downloaded some PDP11 programming manuals and read them over several 
days and come to the conclusion the the PDP11 is not a good choice 
because is has features that a lot of modern 16 bit device do not 
possess mostly in the area of addressing modes, but also unique 
instructions.

The process also impressed me why I used to love the PDP11 when I first 
started working with computers, my first computer I worked with was the 
PDP8e and the PDP11 was such a refreshing improvement, now the 64KB 
direct addressing limit is a pain.

  Right off the bat on the PDP11 all registers are equal so any register 
has all addressing modes, that is inefficient to implement in modern 
CPUs. The PDP11 also has independent addressing for each of two operands 
so for example an ADD instruction can have both sources to use indexed 
modes  for the data for memory to memory operation while most modern 
CPUs uses a register as one of the sources/destination and the other one 
can be indexed but not both so in some cases it takes two instructions 
to do the same as one PDP11 instruction, not the end of the world but it 
makes things more complicated.

So the choices are;

1, To map one instruction to many in some cases and use the PDP11 
instruction set.
2. Use a more limited CPU like the MSP430 as a guide to the instructions 
instead.
3. Just invent my own mnemonics like the Go language that maps closely 
to existing CPUs.
4. Just plain create the primitives in native assembler like it's always 
been done.

I still see an advantage to use a PAC (1-3) coding as a lot of code 
written in it is easily portable to other 16 bit CPUs.

More reading and comparing is required so I will play some more with the 
PDP11 to modern CPU instruct instruction mapping to see how practical it 
all is.

This whole project is getting more complicated and messy than 
anticipated, such is life.

-- 
Cecil - k5nwa

Thread

Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-26 14:49 -0500
  Re: Forth Implementations advantages and disadvantages. minforth@arcor.de - 2017-05-26 13:17 -0700
    Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-26 17:53 -0500
      Re: Forth Implementations advantages and disadvantages. Raimond Dragomir <raimond.dragomir@gmail.com> - 2017-05-26 22:31 -0700
        Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-27 00:57 -0500
  Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-27 01:09 -0400
    Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-27 00:59 -0500
      Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-27 02:09 -0400
        Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-27 09:35 -0500
          Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-27 12:22 -0400
            Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-27 11:53 -0500
              Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-27 13:13 -0400
              Re: Forth Implementations advantages and disadvantages. David Schultz <abuse@127.0.0.1> - 2017-05-27 12:24 -0500
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-27 13:13 -0500
                Re: Forth Implementations advantages and disadvantages. David Schultz <abuse@127.0.0.1> - 2017-05-27 13:33 -0500
                Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-27 14:53 -0400
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-27 14:44 -0500
                Re: Forth Implementations advantages and disadvantages. albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-05-28 10:09 +0200
                Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-28 12:57 -0400
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-28 12:14 -0500
                Re: Forth Implementations advantages and disadvantages. Paul Rubin <no.email@nospam.invalid> - 2017-05-28 16:11 -0700
                Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-29 02:11 -0400
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-29 01:54 -0500
                Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-29 03:22 -0400
    Re: Forth Implementations advantages and disadvantages. Joel Rees <joel.rees@gmail.com> - 2017-05-28 15:46 -0700
  Re: Forth Implementations advantages and disadvantages. Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-27 01:23 -0500
    Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-27 09:29 -0500
      Re: Forth Implementations advantages and disadvantages. Paul Rubin <no.email@nospam.invalid> - 2017-05-27 11:36 -0700
        Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-27 14:25 -0500
      Re: Forth Implementations advantages and disadvantages. Rod Pemberton <NeedNotReplyHere@xrsevnneqk.cem> - 2017-05-27 21:58 -0400
    Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-05-27 11:20 -0700
      Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-27 15:20 -0400
      Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-27 14:20 -0500
        Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-27 18:33 -0400
          Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-27 18:50 -0500
            Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-27 20:13 -0400
          Re: Forth Implementations advantages and disadvantages. albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-05-28 10:23 +0200
            Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-28 12:26 -0500
              Re: Forth Implementations advantages and disadvantages. Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-30 04:22 -0500
                Re: Forth Implementations advantages and disadvantages. albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-05-30 11:49 +0200
                Re: Forth Implementations advantages and disadvantages. Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-05-30 05:07 -0500
                Re: Forth Implementations advantages and disadvantages. Lars Brinkhoff <lars.spam@nocrew.org> - 2017-05-30 18:58 +0200
            Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-28 12:28 -0500
              Re: Forth Implementations advantages and disadvantages. albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-05-28 20:14 +0200
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-28 14:08 -0500
                Re: Forth Implementations advantages and disadvantages. albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-05-29 10:52 +0200
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-29 12:50 -0500
                Re: Forth Implementations advantages and disadvantages. Alex <alex@rivadpm.com> - 2017-05-29 19:06 +0100
        Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-05-27 20:00 -0700
          Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-27 22:29 -0500
            Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-05-27 22:10 -0700
              Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-28 11:22 -0500
                Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-05-28 14:45 -0700
                Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-05-28 18:25 -0700
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-28 21:43 -0500
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-06-01 11:27 -0500
                Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-06-01 12:50 -0400
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-06-01 12:47 -0500
                Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-06-01 16:23 -0400
                Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-06-01 16:32 -0400
                Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-06-01 12:08 -0700
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-06-01 21:47 -0500
                Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-06-02 06:34 -0700
                Re: Forth Implementations advantages and disadvantages. foxaudioresearch@gmail.com - 2017-06-02 07:13 -0700
                Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-06-02 07:57 -0700
                Re: Forth Implementations advantages and disadvantages. albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-06-03 02:17 +0200
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-28 21:07 -0500
                Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-05-28 21:48 -0700
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-29 00:52 -0500
                Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-05-29 09:17 -0700
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-29 12:16 -0500
                Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-05-29 19:21 -0700
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-29 23:13 -0500
                Re: Forth Implementations advantages and disadvantages. Paul Rubin <no.email@nospam.invalid> - 2017-05-30 01:07 -0700
                Re: Forth Implementations advantages and disadvantages. Alex <alex@rivadpm.com> - 2017-05-30 15:54 +0100
                Re: Forth Implementations advantages and disadvantages. Alex <alex@rivadpm.com> - 2017-05-29 19:02 +0100
                Re: Forth Implementations advantages and disadvantages. Raimond Dragomir <raimond.dragomir@gmail.com> - 2017-05-29 11:06 -0700
                Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-05-29 19:29 -0700
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-29 23:01 -0500
                Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-05-30 14:53 -0700
                Re: Forth Implementations advantages and disadvantages. Paul Rubin <no.email@nospam.invalid> - 2017-05-29 13:59 -0700
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-29 17:03 -0500
                Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-05-29 19:37 -0700
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-29 22:52 -0500
            Re: Forth Implementations advantages and disadvantages. Mark Wills <markwills1970@gmail.com> - 2017-05-28 11:49 -0700
              Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-28 14:12 -0500
              Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-29 02:35 -0400
          Re: Forth Implementations advantages and disadvantages. jim.brakefield@ieee.org - 2017-05-27 21:04 -0700
            Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-05-27 21:56 -0700
              Re: Forth Implementations advantages and disadvantages. jim.brakefield@ieee.org - 2017-05-28 01:10 -0700
                Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-28 13:21 -0400
                Re: Forth Implementations advantages and disadvantages. jim.brakefield@ieee.org - 2017-05-28 11:53 -0700
                Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-05-28 15:09 -0700
                Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-29 02:40 -0400
                Re: Forth Implementations advantages and disadvantages. jim.brakefield@ieee.org - 2017-05-29 13:10 -0700
                Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-30 00:57 -0400
          Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-28 02:17 -0400
            Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-28 11:50 -0500
              Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-28 13:52 -0400
                Re: Forth Implementations advantages and disadvantages. Cecil Bayona <cbayona@cbayona.com> - 2017-05-28 13:47 -0500
                Re: Forth Implementations advantages and disadvantages. rickman <gnuarm@gmail.com> - 2017-05-29 03:19 -0400
              Re: Forth Implementations advantages and disadvantages. hughaguilar96@gmail.com - 2017-05-28 15:40 -0700
  Re: Forth Implementations advantages and disadvantages. Joel Rees <joel.rees@gmail.com> - 2017-05-28 16:31 -0700
    Re: Forth Implementations advantages and disadvantages. Joel Rees <joel.rees@gmail.com> - 2017-05-28 20:17 -0700
      Opinions on a C language header for words? Joel Rees <joel.rees@gmail.com> - 2017-05-28 21:38 -0700

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