Re: 32-bit vs. 64-bit x86 Speed

haberg@math.su.se (Hans Aberg)
23 Apr 2007 07:53:17 -0400

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Re: 32-bit vs. 64-bit x86 Speed dot@dotat.at (Tony Finch) (2007-04-13)
Re: 32-bit vs. 64-bit x86 Speed kenney@cix.compulink.co.uk (2007-04-13)
Re: 32-bit vs. 64-bit x86 Speed DrDiettrich1@aol.com (Hans-Peter Diettrich) (2007-04-14)
Re: 32-bit vs. 64-bit x86 Speed DrDiettrich1@aol.com (Hans-Peter Diettrich) (2007-04-14)
Re: 32-bit vs. 64-bit x86 Speed gah@ugcs.caltech.edu (glen herrmannsfeldt) (2007-04-18)
Re: 32-bit vs. 64-bit x86 Speed haberg@math.su.se (2007-04-23)
Re: 32-bit vs. 64-bit x86 Speed haberg@math.su.se (2007-04-23)
Re: 32-bit vs. 64-bit x86 Speed anton@mips.complang.tuwien.ac.at (2007-04-25)
Re: 32-bit vs. 64-bit x86 Speed haberg@math.su.se (2007-04-26)
Re: 32-bit vs. 64-bit x86 Speed haberg@math.su.se (2007-04-27)
Re: 32-bit vs. 64-bit x86 Speed jon@ffconsultancy.com (Jon Harrop) (2007-04-28)
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From: haberg@math.su.se (Hans Aberg)
Newsgroups: comp.compilers
Date: 23 Apr 2007 07:53:17 -0400
Organization: Virgo Supercluster
References: 07-04-031 07-04-045
Keywords: architecture, performance
Posted-Date: 23 Apr 2007 07:53:17 EDT

  George Peter Staplin <georgeps@xmission.com> wrote:


> This is an interesting claim. I've heard from several people that the
> 64-bit x86-64 architecture can be slower with some code patterns.


>From what I have heard, a 32-bit program compiled for a 64-bit CPU, will
in effect run in something alike 32-bit emulation mode. (A deliberate move
in the design of the 64-bit architecture, in order to avoid portability
problems.) So unless it actually has new code, directly rewritten as to
take advantage of the 64-bit architecture, it will in fact run somewhat
slower (of the CPU frequencies are the same).


If the program calls routines that are especially written for the 64-bit
architecture, for example number crunching, the speedup can be
significant.


    Hans Aberg



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