Re: Forth without integer data stack. It is even better!

From	anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups	comp.lang.forth
Subject	Re: Forth without integer data stack. It is even better!
Date	2015-08-18 06:25 +0000
Organization	Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID	<2015Aug18.082553@mips.complang.tuwien.ac.at> (permalink)
References	<ac218bc6-a9cb-47da-b69f-7a612373c302@googlegroups.com> <bbda7b81-5245-4ba3-946b-a9f622b5ee72@googlegroups.com> <5e8b89ea-0fe6-43d4-a067-536d1c2d5125@googlegroups.com> <mqudct$vbn$1@dont-email.me> <256b5010-a417-4058-a8bd-a8bd6fe2bcb7@googlegroups.com>

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Michael Barry <barrym95838@yahoo.com> writes:
>The point I was clumsily trying to make is that the physical address
> sent to access RAM can't be just the mantissa, because normalization
> would cause many different float values to have the same mantissa but
> a different exponent.  So some translation would be required rather
> than just slapping the mantissa on the address bus.  Just slapping the
> full-width float on the address bus would probably guarantee that
> every float address was unique, at least in one direction, but would
> be non-linear, so I don't think that would be a satisfactory technique
> either.

One could require IEEE FP numbers, and then represent addresses with
denormal numbers, and then we can use the FP number directly as
address without conversion to integer first.  However, then CHAR+
would not be 1 +, but ULP +; finally it would make sense that we have
CHARS and CHAR+, but a lot of existing code would not work (but most
of that probably would not work with the other option, either).

The other big disadvantage is that denormals are reportedly slow or
very slow (as in, causing a trap and performing the computation in
software) on a number of machines; not sure how the performance on
currently popular hardware is, though.

Even on hardware with fast denormals, the advantage of this scheme
would not be as big as one may think, though.  The slow thing is not
the conversion from FP to integers itself, but getting the datum from
the FP registers in the FP unit to the integer registers in the
integer unit.  In the old Pentium 4 (Williamette) times, integer
shifts were expensive, because the integers were shipped over to the
FPU, then shifted, and then shipped back; the shipping crossed several
clock domains, losing a cycle at every border.  This was at 2000MHz,
now we are at 4000MHz, and the clock domains are probably even smaller
than then.

- anton
-- 
M. Anton Ertl  http://www.complang.tuwien.ac.at/anton/home.html
comp.lang.forth FAQs: http://www.complang.tuwien.ac.at/forth/faq/toc.html
     New standard: http://www.forth200x.org/forth200x.html
   EuroForth 2015: http://www.mpeforth.com/euroforth2015/euroforth2015.htm

Thread

Forth without integer data stack. It is even better! "Ilya V. Vasilyev" <arvi1973@gmail.com> - 2015-08-15 19:22 -0700
  Re: Forth without integer data stack. It is even better! hughaguilar96@gmail.com - 2015-08-15 20:42 -0700
    Re: Forth without integer data stack. It is even better! "Ilya V. Vasilyev" <arvi1973@gmail.com> - 2015-08-16 02:13 -0700
      Re: Forth without integer data stack. It is even better! hughaguilar96@gmail.com - 2015-08-18 12:09 -0700
        Re: Forth without integer data stack. It is even better! Michael Barry <barrym95838@yahoo.com> - 2015-08-18 15:33 -0700
          Re: Forth without integer data stack. It is even better! Michael Barry <barrym95838@yahoo.com> - 2015-08-18 16:18 -0700
            Re: Forth without integer data stack. It is even better! anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-08-19 08:22 +0000
        Re: Forth without integer data stack. It is even better! "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-08-19 03:38 -0400
        Re: Forth without integer data stack. It is even better! "Ilya V. Vasilyev" <arvi1973@gmail.com> - 2015-09-19 17:21 -0700
          Re: Forth without integer data stack. It is even better! hughaguilar96@gmail.com - 2015-09-19 21:07 -0700
  Re: Forth without integer data stack. It is even better! "WJ" <w_a_x_man@yahoo.com> - 2015-08-16 06:52 +0000
  Re: Forth without integer data stack. It is even better! Roelf Toxopeus <rt4all@notthis.hetnet.nl> - 2015-08-16 14:19 +0200
    Re: Forth without integer data stack. It is even better! Mark Wills <markwills1970@gmail.com> - 2015-08-16 05:52 -0700
      Re: Forth without integer data stack. It is even better! hughaguilar96@gmail.com - 2015-08-16 14:42 -0700
        Re: Forth without integer data stack. It is even better! dylan.mcnamee@gmail.com - 2015-09-21 12:02 -0700
          Re: Forth without integer data stack. It is even better! Bernd Paysan <bernd.paysan@gmx.de> - 2015-09-22 00:34 +0200
      Re: Forth without integer data stack. It is even better! "WJ" <w_a_x_man@yahoo.com> - 2015-09-26 19:18 +0000
    Re: Forth without integer data stack. It is even better! hughaguilar96@gmail.com - 2015-08-16 12:08 -0700
      Re: Forth without integer data stack. It is even better! rickman <gnuarm@gmail.com> - 2015-08-16 15:17 -0400
  Re: Forth without integer data stack. It is even better! anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-08-16 13:47 +0000
    Re: Forth without integer data stack. It is even better! Paul Rubin <no.email@nospam.invalid> - 2015-08-16 07:54 -0700
      Re: Forth without integer data stack. It is even better! anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-08-16 15:04 +0000
        Re: Forth without integer data stack. It is even better! Bernd Paysan <bernd.paysan@gmx.de> - 2015-08-16 23:56 +0200
          Re: Forth without integer data stack. It is even better! Richard Owlett <rowlett@cloud85.net> - 2015-08-17 05:57 -0500
            Re: Forth without integer data stack. It is even better! Coos Haak <chforth@hccnet.nl> - 2015-08-17 13:52 +0200
              Re: Forth without integer data stack. It is even better! Mark Wills <markwills1970@gmail.com> - 2015-08-17 05:00 -0700
            Re: Forth without integer data stack. It is even better! anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-08-17 12:03 +0000
              Re: Forth without integer data stack. It is even better! Mark Wills <markwills1970@gmail.com> - 2015-08-17 05:29 -0700
                Re: Forth without integer data stack. It is even better! anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-08-18 09:10 +0000
          Re: Forth without integer data stack. It is even better! Roelf Toxopeus <rt4all@notthis.hetnet.nl> - 2015-08-17 14:50 +0200
            Re: Forth without integer data stack. It is even better! Bernd Paysan <bernd.paysan@gmx.de> - 2015-08-17 19:42 +0200
              Re: Forth without integer data stack. It is even better! Roelf Toxopeus <rt4all@notthis.hetnet.nl> - 2015-08-17 23:16 +0200
                Re: Forth without integer data stack. It is even better! Bernd Paysan <bernd.paysan@gmx.de> - 2015-08-18 01:00 +0200
                Re: Forth without integer data stack. It is even better! Bernd Paysan <bernd.paysan@gmx.de> - 2015-08-18 01:17 +0200
                Re: Forth without integer data stack. It is even better! Roelf Toxopeus <rt4all@notthis.hetnet.nl> - 2015-08-18 10:12 +0200
              Re: Forth without integer data stack. It is even better! Александр Стадниченко <stadnichenko.a.s@gmail.com> - 2015-09-26 08:12 -0700
              Re: Forth without integer data stack. It is even better! Александр Стадниченко <stadnichenko.a.s@gmail.com> - 2015-09-26 08:35 -0700
                Re: Forth without integer data stack. It is even better! Bernd Paysan <bernd.paysan@gmx.de> - 2015-09-26 21:23 +0200
                Re: Forth without integer data stack. It is even better! Александр Стадниченко <stadnichenko.a.s@gmail.com> - 2015-09-27 09:55 -0700
                Re: Forth without integer data stack. It is even better! Александр Стадниченко <stadnichenko.a.s@gmail.com> - 2015-09-27 10:00 -0700
    Re: Forth without integer data stack. It is even better! mhx@iae.nl - 2015-08-16 08:37 -0700
  Re: Forth without integer data stack. It is even better! Michael Barry <barrym95838@yahoo.com> - 2015-08-17 18:28 -0700
    Re: Forth without integer data stack. It is even better! hughaguilar96@gmail.com - 2015-08-17 20:17 -0700
      Re: Forth without integer data stack. It is even better! rickman <gnuarm@gmail.com> - 2015-08-18 00:49 -0400
        Re: Forth without integer data stack. It is even better! Michael Barry <barrym95838@yahoo.com> - 2015-08-17 23:00 -0700
          Re: Forth without integer data stack. It is even better! anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-08-18 06:25 +0000
            Re: Forth without integer data stack. It is even better! hughaguilar96@gmail.com - 2015-08-18 08:39 -0700
              Re: Forth without integer data stack. It is even better! rickman <gnuarm@gmail.com> - 2015-08-18 12:09 -0400
  Re: Forth without integer data stack. It is even better! Ilya Tarasov <ilya74.tarasov@gmail.com> - 2015-08-18 01:31 -0700
    Re: Forth without integer data stack. It is even better! "Ilya V. Vasilyev" <arvi1973@gmail.com> - 2015-09-12 17:47 -0700
      Re: Forth without integer data stack. It is even better! hughaguilar96@gmail.com - 2015-09-12 18:06 -0700

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