Re: Forth Implementations advantages and disadvantages.

From	rickman <gnuarm@gmail.com>
Newsgroups	comp.lang.forth
Subject	Re: Forth Implementations advantages and disadvantages.
Date	2017-05-28 13:52 -0400
Organization	A noiseless patient Spider
Message-ID	<ogf2ir$leh$1@dont-email.me> (permalink)
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Cecil Bayona wrote on 5/28/2017 12:50 PM:
> On 5/28/2017 1:17 AM, rickman wrote:
>> hughaguilar96@gmail.com wrote on 5/27/2017 11:00 PM:
>
>>> The PDP11 would be another possibility. It has these points in favor of it:
>>>
>>> 1.) the PDP11 has 8 registers rather than 16, which makes it a good
>>> choice for an FPGA (the number of registers is the primary factor in how
>>> much chip resources are needed, and how expensive the FPGA is).
>>
>> Not trying to get on your case, but you are talking outside your realm of
>> familiarity.  Many FPGAs provide small RAMs for exactly this sort of
>> thing. In Xilinx derived parts the look up tables used to create logic can
>> be used as register files.  Each one is a 16x1 RAM (or in newer parts
>> 64x1).  So restricting the register count to 8 is of little value in
>> conserving resources.  There are many other things that impact resources
>> in a much greater way.
>>
>>
>
> All kinds of useful information is coming out of this topic, I been using
> Lattice FPGAs so far because its a decent tool for low $, but I did buy one
> Xilinx board for more serious work and it's an Artix 7 board, with a lot of
> LUTS and Memory for use in larger CPUs. That is nice to know in case I want
> to create a more conventional Register based CPU.

All of the Lattice FPGAs have the LUT RAM available as distributed RAM like 
the Xilinx parts.  The main Lattice FPGA lines are from licenses obtained by 
buying the ORCA line of FPGAs from Lucent.  These licenses in turn were 
bought by Lucent from Xilinx at a time when Lucent was second sourcing the 
basic XC3000 and maybe the XC4000 devices.

The iCE40 parts are from Silicon Blue bought some years ago.  The basic 
design patents on Xilinx FPGAs have expired so many functions of Xilinx LUTs 
are available to all including distributed memory.

>>> 2.) There are public-domain implementations of the PDP11 available in
>>> Verilog, which is not true of the MSP430.
>>>
>>> 3.) The PDP11 has a very orthogonal and straight-forward instruction set,
>>> which is not true of the 8086, although it is true of the MSP430.
>>
>> I don't think the issue would be how nice the "virtual" instruction set
>> is. The issue is how well it will map to the plurality of targets.  Most
>> FPGA targets will be stack machines which don't even have register files.
>> Most likely programming a stack machine using an assembly language for a
>> register based processor would be difficult to make efficient.
>
> Stack machines is my current line of interest so far the richest machine
> I've used uses the following registers;
>
> TOS top of Data Stack
> TRS top of Return Stack
> W a temporary register
> IX an Index register to use with memory access specially in accessing arrays
> of data.
> IP Instruction Pointer
>
> Add to that a Data and Return Stack but those are not registers but their
> pointers use a small register not directly accessible.
>
> Not a whole lot of registers specially when compared to a MSP430 CPU with 16
> general registers, or an ARM CPU with 32 general registers.

Big difference...  The registers in a stack machine need to be separate, so 
they use FFs for the registers and LUTs for the input and output muxes.  A 
RAM is a bunch of registers with output muxes to share the output bus.  A 
register file can be efficiently implemented in a small RAM which utilizes 
the internal muxes rather than LUTs.

Regardless of how many registers a design has, the real driver of logic 
usage is usually muxes.  You can have one register (top of data stack for 
example) which is fed by many sources and the mux will end up being huge.  I 
know this from experience... ;)

The way to keep your design small and efficient is to focus on the micro-ops 
required to implement an instruction to keep these interconnects to a minimum.

The reason why an ARM CPU in an FPGA will be much bigger than an MSP430 is 
the complexity of interconnections.  I think it is the M1 that is intended 
for FPGA usage.  I expect this is very stripped own using more cycles with 
less happening in each one compared to an M0.

>> Actually, it isn't even just targeting multiple processors with the
>> programming language.  The issue is writing a Forth in assembly for a
>> register based machine and then translating that into an efficient Forth
>> for a stack based machine.  Maybe this can be done.  But I don't see it as
>> being a better solution than just taking the easy route and programming
>> the Forth in assembly for the given target.
>>
>
> Using PAC (Portable Assembler Code) mnemonics when moving the code to
> another CPU the primitives and other assembler code does not need to be
> changed, only the assembler needs to be changed and that would need changes
> no matter what scheme one uses, so it is simpler to port using a PAC
> assembler. It's not the traditional way where you have to re-write all the
> assembly code but times are changing we are not in the 70s anymore.

You seem to be laser focused on the idea that rewriting the tool has to be 
easier than rewriting the code.  I don't know of any portable assemblers 
that work the way you describe.  So you will need to write this from scratch.

> I tend to think that this is a superior way to write a Forth that is
> efficient and easy to port qualities that with traditional assemble code are
> at odds with each other. Mind you no matter what one uses there are some CPU
> specific items that need to be update such clock management and I/O but
> those need changing with a new CPU no matter what way one uses so it
> something to be dealt with.

I don't see any advantage at all.  Either way you need to generate native 
code for the processor you are using.  One way you recode a few Forth words 
which gives you native code *and* gives you an opportunity to optimize the 
code easily.  The other way you have existing "portable" assembler code 
which now has to be translated/compiled to native code by a tool that needs 
to be rewritten for the target processor.  Then if you want optimized code 
you likely need to rewrite the "portable" assembly code.

I am ready to return to my self-assigned task of documenting Mecrisp on the 
MSP430.  Let me know how your project goes.  If you need any advice on FPGA 
CPUs, I'm happy to lend my experience.

-- 

Rick C

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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