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Re: Combining Practicality with Perfection

From MitchAlsup <user5857@newsgrouper.org.invalid>
Newsgroups comp.arch
Subject Re: Combining Practicality with Perfection
References (4 earlier) <10mj5el$1gf9$1@gal.iecc.com> <1770861898-5857@newsgrouper.org> <2026Feb12.094503@mips.complang.tuwien.ac.at> <1770916156-5857@newsgrouper.org> <10n6gph$3bat5$1@dont-email.me>
Date 2026-02-19 17:30 +0000
Message-ID <1771522250-5857@newsgrouper.org> (permalink)

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BGB <cr88192@gmail.com> posted:

> On 2/12/2026 11:09 AM, MitchAlsup wrote:
> > 
> > anton@mips.complang.tuwien.ac.at (Anton Ertl) posted:
> > 
> >> MitchAlsup <user5857@newsgrouper.org.invalid> writes:
> >>> {{One can STILL argue whether
> >>> deNormals were a plus or a minus in IEEE}}
> >>
> >> I am surprised to read that from you, who has always written that
> >> denormals can be implemented cheaply and efficiently in hardware.  The
> >> additional hardware cost (or the cost of trapping and software
> >> emulation) has been the only argument against denormals that I ever
> >> encountered.
> > 
> > It is only after IEEE 754-2008 came with FMAC that deNormals became
> > a low cost addition. {And that has been my point--you seem to have
> > forgotten the -2008 part or the argument}
> 
> And, can note, this is assuming that one actually pays the cost of 
> native hardware FMAC.
> 
It is exceedingly difficult to get an IEEE quality rounded result if
not done in HW.
> 
> Well, and the secondary irony that it is mainly cost-added for FMUL, 
> whereas FADD almost invariably has the necessary support hardware already.
> 
> But:
>    FMUL is expensive operation + cheap normalizer (if no denormals);
>    FADD is cheap operation with expensive normalizer.
> 
> FMAC then is gluing the costs of the two units together, but:
>    With roughly the latency of both;
>    The need to be significantly wider internally to deal with some cases.

The add stage after the multiplication tree is <essentially> 2× as wide.
FMUL needs a 108-bit 2-input adder
FMAC needs a 160-bit 3-input adder and a 52-bit incrementor.
The multiplication tree is the same, normalizer is larger.

> 
> So, FMAC is a single unit that costs more than both units taken 
> separately, and with a higher latency.

Prior RISC processors did FMUL in 3-4 cycles (mostly 4).
Later RISC processors and x86 did FMAC in 4-cycles (occasionally 5).

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Combining Practicality with Perfection John Savard <quadibloc@invalid.invalid> - 2026-01-31 18:28 +0000
  Re: Combining Practicality with Perfection jgd@cix.co.uk (John Dallman) - 2026-01-31 22:36 +0000
  Re: Combining Practicality with Perfection MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-02-05 01:57 +0000
    Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-05 06:06 +0000
      Re: Combining Practicality with Perfection Robert Finch <robfi680@gmail.com> - 2026-02-05 08:10 -0500
      Re: Combining Practicality with Perfection scott@slp53.sl.home (Scott Lurndal) - 2026-02-05 14:50 +0000
      Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-05 23:58 +0000
        Re: Combining Practicality with Perfection jgd@cix.co.uk (John Dallman) - 2026-02-06 16:37 +0000
          Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-06 22:32 +0000
            Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-06 22:34 +0000
            Re: Combining Practicality with Perfection MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-02-07 00:57 +0000
              Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-07 02:45 +0000
          Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-06 22:40 +0000
        Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-09 22:46 +0000
          Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-10 03:49 +0000
            Re: Combining Practicality with Perfection MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-02-10 19:10 +0000
              Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-11 23:04 +0000
                Re: Combining Practicality with Perfection MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-02-11 23:55 +0000
                Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-12 06:04 +0000
                Re: Combining Practicality with Perfection quadibloc@invalid.com (John Savard) - 2026-10-24 00:22 +0000
                Re: Combining Practicality with Perfection MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-10-24 19:32 +0000
                Re: Combining Practicality with Perfection jgd@cix.co.uk (John Dallman) - 2026-10-25 06:00 +0000
                Re: Combining Practicality with Perfection quadibloc@invalid.com (John Savard) - 2026-10-25 17:38 +0000
                Re: Combining Practicality with Perfection Stephen Fuld <sfuld@alumni.cmu.edu.invalid> - 2026-10-25 22:43 -0700
                Re: Combining Practicality with Perfection jgd@cix.co.uk (John Dallman) - 2026-10-26 09:35 +0000
                Re: Combining Practicality with Perfection John Levine <johnl@taugh.com> - 2026-10-26 19:53 +0000
                Re: Combining Practicality with Perfection MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-10-26 13:40 +0000
                Re: Combining Practicality with Perfection quadibloc@invalid.com (John Savard) - 2026-10-26 22:05 +0000
                Re: Combining Practicality with Perfection quadibloc@invalid.com (John Savard) - 2026-10-26 22:12 +0000
                Re: Combining Practicality with Perfection Stephen Fuld <sfuld@alumni.cmu.edu.invalid> - 2026-10-26 20:13 -0700
                Re: Combining Practicality with Perfection quadibloc@invalid.com (John Savard) - 2026-10-27 14:30 +0000
                Re: Combining Practicality with Perfection quadibloc@invalid.com (John Savard) - 2026-10-26 22:09 +0000
                Re: Combining Practicality with Perfection EricP <ThatWouldBeTelling@thevillage.com> - 2026-10-26 18:20 -0400
                Re: Combining Practicality with Perfection quadibloc@invalid.com (John Savard) - 2026-10-27 03:00 +0000
                Re: Combining Practicality with Perfection antispam@fricas.org (Waldek Hebisch) - 2026-10-26 22:51 +0000
                Re: Combining Practicality with Perfection John Levine <johnl@taugh.com> - 2026-10-25 18:47 +0000
                Re: Combining Practicality with Perfection David Schultz <david.schultz@earthlink.net> - 2026-02-11 17:57 -0600
                Re: Combining Practicality with Perfection John Levine <johnl@taugh.com> - 2026-02-12 00:04 +0000
                Re: Combining Practicality with Perfection MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-02-12 02:04 +0000
                Re: Combining Practicality with Perfection John Levine <johnl@taugh.com> - 2026-02-12 03:31 +0000
                Hex floating point (was: Combining Practicality with Perfection) Thomas Koenig <tkoenig@netcologne.de> - 2026-02-15 16:53 +0000
                Re: Combining Practicality with Perfection anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2026-02-12 08:45 +0000
                Re: Combining Practicality with Perfection MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-02-12 17:09 +0000
                Re: Combining Practicality with Perfection Terje Mathisen <terje.mathisen@tmsw.no> - 2026-02-14 18:03 +0100
                Re: Combining Practicality with Perfection BGB <cr88192@gmail.com> - 2026-02-19 02:10 -0600
                Re: Combining Practicality with Perfection MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-02-19 17:30 +0000
                Re: Combining Practicality with Perfection Michael S <already5chosen@yahoo.com> - 2026-02-19 20:15 +0200
                Re: Combining Practicality with Perfection MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-02-19 19:55 +0000
                Re: Combining Practicality with Perfection BGB <cr88192@gmail.com> - 2026-02-20 05:08 -0600
                Re: Combining Practicality with Perfection Terje Mathisen <terje.mathisen@tmsw.no> - 2026-02-20 15:22 +0100
                Re: Combining Practicality with Perfection BGB <cr88192@gmail.com> - 2026-02-20 15:26 -0600
                Re: Combining Practicality with Perfection Paul Clayton <paaronclayton@gmail.com> - 2026-02-21 20:27 -0500
                Re: Combining Practicality with Perfection Michael S <already5chosen@yahoo.com> - 2026-02-12 10:49 +0200
                Re: Combining Practicality with Perfection MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-02-12 17:10 +0000
                Re: Combining Practicality with Perfection Michael S <already5chosen@yahoo.com> - 2026-02-12 23:38 +0200
                Re: Combining Practicality with Perfection Terje Mathisen <terje.mathisen@tmsw.no> - 2026-02-12 14:28 +0100
                Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-12 05:51 +0000
                Re: Combining Practicality with Perfection Michael S <already5chosen@yahoo.com> - 2026-02-12 10:53 +0200
                Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-12 18:40 +0000
                Re: Combining Practicality with Perfection MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-02-12 20:02 +0000
                Re: Combining Practicality with Perfection MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-02-12 20:33 +0000
                Re: Combining Practicality with Perfection Stephen Fuld <sfuld@alumni.cmu.edu.invalid> - 2026-02-11 19:50 -0800
                Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-12 05:55 +0000
                Re: Combining Practicality with Perfection Stephen Fuld <sfuld@alumni.cmu.edu.invalid> - 2026-02-12 08:40 -0800
                Re: Combining Practicality with Perfection scott@slp53.sl.home (Scott Lurndal) - 2026-02-12 16:51 +0000
                Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-12 18:49 +0000
                Re: Combining Practicality with Perfection scott@slp53.sl.home (Scott Lurndal) - 2026-02-12 15:54 +0000
                Re: Combining Practicality with Perfection Stephen Fuld <sfuld@alumni.cmu.edu.invalid> - 2026-02-12 08:52 -0800
                Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-12 18:37 +0000
                Re: Combining Practicality with Perfection antispam@fricas.org (Waldek Hebisch) - 2026-02-14 16:33 +0000
                Re: floating pain, Combining Practicality with Perfection John Levine <johnl@taugh.com> - 2026-02-14 18:12 +0000
                Re: floating pain, Combining Practicality with Perfection antispam@fricas.org (Waldek Hebisch) - 2026-02-17 01:16 +0000
                Re: floating pain, Combining Practicality with Perfection John Levine <johnl@taugh.com> - 2026-02-17 01:24 +0000
                Re: floating pain, Combining Practicality with Perfection antispam@fricas.org (Waldek Hebisch) - 2026-02-17 16:21 +0000
                Re: floating pain, Combining Practicality with Perfection John Levine <johnl@taugh.com> - 2026-02-17 19:20 +0000
                Re: floating pain, Combining Practicality with Perfection antispam@fricas.org (Waldek Hebisch) - 2026-02-17 19:52 +0000
                Re: floating pain, Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-17 19:09 +0000
                Re: Combining Practicality with Perfection jgd@cix.co.uk (John Dallman) - 2026-02-15 14:37 +0000
                Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-17 18:57 +0000
                Re: Combining Practicality with Perfection antispam@fricas.org (Waldek Hebisch) - 2026-02-17 20:43 +0000
                Re: Combining Practicality with Perfection MitchAlsup <user5857@newsgrouper.org.invalid> - 2026-02-18 00:50 +0000
                Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-18 08:52 +0000
                Re: Combining Practicality with Perfection Robert Finch <robfi680@gmail.com> - 2026-02-18 08:40 -0500
                Re: Combining Practicality with Perfection quadi <quadibloc@ca.invalid> - 2026-02-20 08:14 +0000
                Re: Combining Practicality with Perfection Thomas Koenig <tkoenig@netcologne.de> - 2026-02-19 18:49 +0000

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