Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.arch > #4764

Re: implementation of unsigned addition on one's complement machines

From torbenm@diku.dk (Torben Ægidius Mogensen)
Newsgroups comp.arch
Subject Re: implementation of unsigned addition on one's complement machines
References <1ca86407-1dbc-452c-af08-1f6d1bb76e24@u9g2000vbx.googlegroups.com> <7z39dqtzi2.fsf@ask.diku.dk>
Date 2011-11-15 10:29 +0100
Message-ID <7z62ilka2u.fsf@ask.diku.dk> (permalink)
Organization SunSITE.dk - Supporting Open source

Show all headers | View raw

torbenm@diku.dk (Torben Ægidius Mogensen) writes:

> Luca Forlizzi <luca.forlizzi@gmail.com> writes:
>
>> How unsigned addition is implemented in one's complement CPUs?
>
> I can't find unsigned addition in the Univac 1100 instruction set (which
> uses one's complement as default and supports sign+magnitude as well).
>
> So I suspect the answer is "It isn't".

However, if you don't overflow, ones-complement addition works fine for
unsigned addition.  The difference between ones-complement addition and
unsigned addition is that, if the addition has a carry out, this is
added back in to the lsb.  So if this never happens, you are O.K.

	Torben

Back to comp.arch | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

implementation of unsigned addition on one's complement machines Luca Forlizzi <luca.forlizzi@gmail.com> - 2011-11-14 07:08 -0800
  Re: implementation of unsigned addition on one's complement machines torbenm@diku.dk (Torben Ægidius Mogensen) - 2011-11-14 17:55 +0100
    Re: implementation of unsigned addition on one's complement machines torbenm@diku.dk (Torben Ægidius Mogensen) - 2011-11-15 10:29 +0100
      Re: implementation of unsigned addition on one's complement machines Luca Forlizzi <luca.forlizzi@gmail.com> - 2011-11-15 02:12 -0800
        Re: implementation of unsigned addition on one's complement machines nmm1@cam.ac.uk - 2011-11-15 10:28 +0000
          Re: implementation of unsigned addition on one's complement machines Luca Forlizzi <luca.forlizzi@gmail.com> - 2011-11-15 03:07 -0800
            Re: implementation of unsigned addition on one's complement machines nmm1@cam.ac.uk - 2011-11-15 11:13 +0000
              Re: implementation of unsigned addition on one's complement machines anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-11-15 17:33 +0000
                Re: implementation of unsigned addition on one's complement machines nmm1@cam.ac.uk - 2011-11-15 18:14 +0000
                Re: implementation of unsigned addition on one's complement machines anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-11-16 09:34 +0000
        Re: implementation of unsigned addition on one's complement machines Michael S <already5chosen@yahoo.com> - 2011-11-16 09:04 -0800
          Re: implementation of unsigned addition on one's complement machines nmm1@cam.ac.uk - 2011-11-16 17:31 +0000
          Re: implementation of unsigned addition on one's complement machines Robert Wessel <robertwessel2@yahoo.com> - 2011-11-16 11:54 -0600
    Re: implementation of unsigned addition on one's complement machines Luca Forlizzi <luca.forlizzi@gmail.com> - 2011-11-15 03:11 -0800
  Re: implementation of unsigned addition on one's complement machines anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2011-11-15 17:26 +0000
    Re: implementation of unsigned addition on one's complement machines Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-11-15 23:12 +0100
      Re: implementation of unsigned addition on one's complement machines Kai Harrekilde-Petersen <khp@harrekilde.dk> - 2011-11-15 23:25 +0100

csiph-web