Re: MISC - Stack Based vs. Register Based

From	"Rod Pemberton" <do_not_have@notemailnotq.cpm>
Newsgroups	comp.lang.forth, comp.arch.fpga
Subject	Re: MISC - Stack Based vs. Register Based
Date	2013-04-01 20:10 -0400
Organization	Aioe.org NNTP Server
Message-ID	<kjd7gp$t0n$1@speranza.aioe.org> (permalink)
References	<kj4vae$msi$1@dont-email.me> <kj7mqk$17p$1@speranza.aioe.org> <5157e1a1$0$6924$e4fe514c@news2.news.xs4all.nl>

Cross-posted to 2 groups.

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"Arlet Ottens" <usenet+5@c-scape.nl> wrote in message
news:5157e1a1$0$6924$e4fe514c@news2.news.xs4all.nl...
> On 03/30/2013 10:54 PM, Rod Pemberton wrote:

> >>
> >> I guess looking at other peoples designs (such as Chuck's)
> >> has changed my perspective over the years so that I am
> >> willing and able to do optimizations in ways I would not have
> >> wanted to do in the past. But I am a bit surprised that there
> >> has been so much emphasis on stack oriented MISC machines
> >> which it may well be that register based MISC designs are
> >> also very efficient, at least if you aren't building them to
> >> service a C compiler or trying to match some ideal RISC
> >> model.
> >>
> >
> > Are those your actual results or did you just reiterate what
> > is on Wikipedia?  Yes, that's a serious question.  Read the
> > MISC page: [link]
> >
> > See ... ?!
>
> It sounds to me rickman is questioning the (unsupported) claims
> on wikipedia that stack based machines have an advantage in size
> and/or simplicity, not reiterating them.
>

Well, you snipped alot of context.  I wouldn't have reformatted
all of it either.

Anyway, what I took from rickman's statements was that he had only
managed to confirm what is already known about MISC according to
Wikipedia.  I.e., what was/is the point?

> > Code density is a CISC concept.  I don't see how it applies to
> > your MISC project.  Increasing code density for a MISC
> > processor means implementing more powerful instructions,
> > i.e., those that do more work, while minimizing bytes in the
> > instruction opcode encoding.  Even if you implement
> > CISC-like instructions, you can't forgo the MISC instructions
> > you already have in order to add the CISC-like instructions.
> > So, to do that, you'll need to increase the size of the
> > instruction set, as well as implement a more complicated
> > instruction decoder.  I.e., that means the processor will no
> > longer be MISC, but MISC+minimal CISC hybrid, or pure
> > CISC...
>
> It is perfectly possible to trade one type of MISC processor for
> another one. The choice between stack and register based is an
> obvious one. If you switch from stack to register based, there's
> no need to keep stack manipulation instructions around.
>

Yes, true.  But, what does eliminating MISC stack instructions and
replacing them with MISC register instructions have to do with the
CISC concept of code density or with CISC instructions? ...

> > Also, you cross-posted to comp.arch.fpga.  While they'll
> > likely be familiar with FPGAs, most there are not going
> > to be familiar with the features of stack-based processors
> > or Forth processors that you discuss indirectly within your
> > post.  They might not be familiar with ancient CISC
> > concepts such as "code density" either, or understand why
> > it was important at one point in time.  E.g., I suspect this
> > Forth related stuff from above won't be widely
> > understood on c.a.f. without clarification:
>
> The design of simple and compact processors is of great interest
> to many FPGA engineers. Plenty of FPGA designs need some
> sort of control processor, and for cost reduction it's important
> to use minimal resources. Like rickman said, this involves a
> careful balance between implementation complexity, speed,
> and code density, while also considering how much work it
> is to write/maintain the software that's running on the
> processor.
>
> Code density is still critically important. Fast memory is
> small, both on FPGA as well as general purpose processors.
>

So, shouldn't he dump the entire MISC instruction set he has, and
implement a CISC instruction set instead?  That's the only way
he's going to get the "critically important" code density, which
I'll take it you rank well above MISC as being important.  Of
course, a CISC instruction set requires a more complicated
instruction decoder ...  So, it seems that either way he proceeds,
he is being contrained by the "minimal resources" of his FPGA.
That was what he stated:

  "My efforts have shown it hard to improve on code density by a
significant degree while simultaneously minimizing the resources
used by the design."

I.e., if the FPGA he is attempting to use is insufficient to do
what he wants or needs, then it's insufficient.  Or, he needs some
new techniques.  He didn't explicitly ask for any though ...

Glen mentioned the numerous address modes of the VAX.  The 6502
also had alot of address modes and had instructions which used
zero-page as a set of fast registers.  I would think that early,
compact designs like the 6502 and Z80 could be useful to rickman.
They had low transistor counts.

Z80   8500 transistors
6502  9000 transistors
8088 29000 transistors (for comparison...)


Rod Pemberton

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Thread

MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-03-29 17:00 -0400
  Re: MISC - Stack Based vs. Register Based glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-03-29 21:43 +0000
    Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-03-29 20:28 -0400
      Re: MISC - Stack Based vs. Register Based glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-03-31 18:34 +0000
        Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-02 09:54 -0400
          Re: MISC - Stack Based vs. Register Based glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-04-02 17:20 +0000
            Re: MISC - Stack Based vs. Register Based David Brown <david@westcontrol.removethisbit.com> - 2013-04-03 09:12 +0200
    Re: MISC - Stack Based vs. Register Based Jon Elson <jmelson@wustl.edu> - 2013-04-01 15:11 -0500
  Re: MISC - Stack Based vs. Register Based AKE <assadebrahim2000@gmail.com> - 2013-03-29 18:19 -0700
    Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-03-30 18:50 -0400
      Re: MISC - Stack Based vs. Register Based Jecel <jecel@merlintec.com> - 2013-04-01 13:18 -0700
        Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-02 10:50 -0400
          Re: MISC - Stack Based vs. Register Based Jecel <jecel@merlintec.com> - 2013-04-02 23:39 -0700
            Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-03 09:54 -0400
              Re: MISC - Stack Based vs. Register Based Jecel <jecel@merlintec.com> - 2013-04-05 14:30 -0700
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-05 17:53 -0400
                Re: MISC - Stack Based vs. Register Based Jecel <jecel@merlintec.com> - 2013-04-06 13:27 -0700
                Re: MISC - Stack Based vs. Register Based Jecel <jecel@merlintec.com> - 2013-04-06 13:37 -0700
        Re: MISC - Stack Based vs. Register Based Paul Rubin <no.email@nospam.invalid> - 2013-04-07 15:21 -0700
          Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-08 01:24 -0400
            Re: MISC - Stack Based vs. Register Based Syd Rumpo <usenet@nononono.co.uk> - 2013-04-08 10:18 +0100
          Re: MISC - Stack Based vs. Register Based Andrew Haley <andrew29@littlepinkcloud.invalid> - 2013-04-08 04:18 -0500
  Re: MISC - Stack Based vs. Register Based Arlet Ottens <usenet+5@c-scape.nl> - 2013-03-30 08:20 +0100
    Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-03-30 19:00 -0400
      Re: MISC - Stack Based vs. Register Based Arlet Ottens <usenet+5@c-scape.nl> - 2013-03-31 13:20 +0200
  Re: MISC - Stack Based vs. Register Based "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-03-30 17:54 -0400
    Re: MISC - Stack Based vs. Register Based Arlet Ottens <usenet+5@c-scape.nl> - 2013-03-31 09:11 +0200
      Re: MISC - Stack Based vs. Register Based "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-04-01 20:10 -0400
        Re: MISC - Stack Based vs. Register Based glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-04-02 00:54 +0000
          Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-02 13:31 -0400
            Re: MISC - Stack Based vs. Register Based glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-04-02 19:03 +0000
        Re: MISC - Stack Based vs. Register Based Arlet Ottens <usenet+5@c-scape.nl> - 2013-04-02 08:25 +0200
          Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-02 13:33 -0400
        Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-02 13:26 -0400
          Re: MISC - Stack Based vs. Register Based "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-04-03 20:34 -0400
            Re: MISC - Stack Based vs. Register Based glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-04-04 02:07 +0000
              Re: MISC - Stack Based vs. Register Based albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-04-04 11:16 +0000
                Re: MISC - Stack Based vs. Register Based Arlet Ottens <usenet+5@c-scape.nl> - 2013-04-04 13:25 +0200
                Re: MISC - Stack Based vs. Register Based glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-04-04 12:44 +0000
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-04 17:04 -0400
                Re: MISC - Stack Based vs. Register Based glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-04-04 21:34 +0000
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-04 19:30 -0400
                Re: MISC - Stack Based vs. Register Based Mark Wills <markrobertwills@yahoo.co.uk> - 2013-04-05 00:41 -0700
                Re: MISC - Stack Based vs. Register Based Alex McDonald <blog@rivadpm.com> - 2013-04-04 15:30 -0700
                Re: MISC - Stack Based vs. Register Based glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-04-04 23:15 +0000
                Re: MISC - Stack Based vs. Register Based Alex McDonald <blog@rivadpm.com> - 2013-04-04 17:26 -0700
                Re: MISC - Stack Based vs. Register Based albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-04-05 01:17 +0000
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-05 18:00 -0400
                Re: MISC - Stack Based vs. Register Based "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-04-08 23:55 -0400
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-04 20:07 -0400
                Re: MISC - Stack Based vs. Register Based Mark Wills <markrobertwills@yahoo.co.uk> - 2013-04-05 00:51 -0700
                Re: MISC - Stack Based vs. Register Based Arlet Ottens <usenet+5@c-scape.nl> - 2013-04-05 14:31 +0200
                Re: MISC - Stack Based vs. Register Based Mark Wills <markrobertwills@yahoo.co.uk> - 2013-04-05 07:33 -0700
                Re: MISC - Stack Based vs. Register Based Arlet Ottens <usenet+5@c-scape.nl> - 2013-04-05 17:01 +0200
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-05 18:25 -0400
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-06 17:44 -0400
                Re: MISC - Stack Based vs. Register Based Brad Eckert <hwfwguy@gmail.com> - 2013-04-05 10:14 -0700
                Re: MISC - Stack Based vs. Register Based Arlet Ottens <usenet+5@c-scape.nl> - 2013-04-05 20:13 +0200
                Re: MISC - Stack Based vs. Register Based Arlet Ottens <usenet+5@c-scape.nl> - 2013-04-05 20:15 +0200
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-05 18:54 -0400
                Re: MISC - Stack Based vs. Register Based Brad Eckert <hwfwguy@gmail.com> - 2013-04-08 09:57 -0700
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-09 10:13 -0400
                Re: MISC - Stack Based vs. Register Based Brad Eckert <hwfwguy@gmail.com> - 2013-04-09 08:55 -0700
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-09 14:40 -0400
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-05 18:49 -0400
                Re: MISC - Stack Based vs. Register Based daveyrotten <danw8804@gmail.com> - 2013-04-09 13:02 -0700
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-09 16:07 -0400
                Re: MISC - Stack Based vs. Register Based daveyrotten <danw8804@gmail.com> - 2013-04-09 13:26 -0700
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-10 00:33 -0400
                Re: MISC - Stack Based vs. Register Based daveyrotten <danw8804@gmail.com> - 2013-04-10 07:08 -0700
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-10 10:13 -0400
                Re: MISC - Stack Based vs. Register Based Sieur de Bienville <morrimichael@gmail.com> - 2013-04-10 21:08 -0700
                Re: MISC - Stack Based vs. Register Based Paul Rubin <no.email@nospam.invalid> - 2013-04-10 22:47 -0700
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-11 16:32 -0400
                Re: MISC - Stack Based vs. Register Based "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-04-18 06:23 -0400
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-18 17:06 -0400
                Re: MISC - Stack Based vs. Register Based glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-04-05 17:33 +0000
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-06 17:37 -0400
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-05 18:08 -0400
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-06 17:32 -0400
                Re: MISC - Stack Based vs. Register Based Brian Davis <brimdavis@aol.com> - 2013-04-07 14:59 -0700
                Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-08 01:16 -0400
                Re: MISC - Stack Based vs. Register Based albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-04-08 09:52 +0000
            Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-03 22:42 -0400
            Re: MISC - Stack Based vs. Register Based Alex McDonald <blog@rivadpm.com> - 2013-04-04 16:07 -0700
              Re: MISC - Stack Based vs. Register Based glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-04-05 04:10 +0000
                Re: MISC - Stack Based vs. Register Based Alex McDonald <blog@rivadpm.com> - 2013-04-04 23:49 -0700
    Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-02 12:04 -0400
      Re: MISC - Stack Based vs. Register Based "Rod Pemberton" <do_not_have@notemailnotq.cpm> - 2013-04-03 20:35 -0400
        Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-04 00:09 -0400
  Re: MISC - Stack Based vs. Register Based the_gavino_himself <visphatesjava@gmail.com> - 2013-04-02 11:17 -0700
  Re: MISC - Stack Based vs. Register Based Syd Rumpo <usenet@nononono.co.uk> - 2013-04-04 09:38 +0100
    Re: MISC - Stack Based vs. Register Based Arlet Ottens <usenet+5@c-scape.nl> - 2013-04-04 11:31 +0200
      Re: MISC - Stack Based vs. Register Based "Elizabeth D. Rather" <erather@forth.com> - 2013-04-04 08:36 -1000
        Re: MISC - Stack Based vs. Register Based Brad Eckert <hwfwguy@gmail.com> - 2013-04-05 10:21 -0700
          Re: MISC - Stack Based vs. Register Based "Elizabeth D. Rather" <erather@forth.com> - 2013-04-05 07:53 -1000
    Re: MISC - Stack Based vs. Register Based glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-04-04 12:49 +0000
      Re: MISC - Stack Based vs. Register Based Arlet Ottens <usenet+5@c-scape.nl> - 2013-04-04 15:02 +0200
    Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-04 18:57 -0400
  Re: MISC - Stack Based vs. Register Based AKE <assadebrahim2000@gmail.com> - 2013-04-05 15:29 -0700
    Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-05 19:32 -0400
      Re: MISC - Stack Based vs. Register Based anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-06 14:16 +0000
        Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-06 15:50 -0400
          Re: MISC - Stack Based vs. Register Based mhx@iae.nl (Marcel Hendrix) - 2013-04-07 01:33 +0200
            Re: MISC - Stack Based vs. Register Based AKE <assadebrahim2000@gmail.com> - 2013-04-07 02:57 -0700
              Re: MISC - Stack Based vs. Register Based stephenXXX@mpeforth.com (Stephen Pelc) - 2013-04-07 11:02 +0000
              Re: MISC - Stack Based vs. Register Based anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-07 13:51 +0000
                Re: MISC - Stack Based vs. Register Based "Elizabeth D. Rather" <erather@forth.com> - 2013-04-07 09:16 -1000
            Re: MISC - Stack Based vs. Register Based anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-07 14:13 +0000
              Re: MISC - Stack Based vs. Register Based mhx@iae.nl (Marcel Hendrix) - 2013-04-07 17:14 +0200
                Re: MISC - Stack Based vs. Register Based anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-07 15:31 +0000
            Re: MISC - Stack Based vs. Register Based Bernd Paysan <bernd.paysan@gmx.de> - 2013-04-08 18:53 +0200
          Re: MISC - Stack Based vs. Register Based anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-04-07 14:22 +0000
  Re: MISC - Stack Based vs. Register Based "WJ" <w_a_x_man@yahoo.com> - 2013-04-14 00:19 +0000
    Re: MISC - Stack Based vs. Register Based rickman <gnuarm@gmail.com> - 2013-04-14 09:44 -0400
    Re: MISC - Stack Based vs. Register Based Brad Eckert <hwfwguy@gmail.com> - 2013-04-15 09:39 -0700
      Re: MISC - Stack Based vs. Register Based Bernd Paysan <bernd.paysan@gmx.de> - 2013-04-15 19:28 +0200

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