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   comp.compilers      Compiler construction, theory, etc. (Mod      2,753 messages   

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   Message 938 of 2,753   
   Hans Aberg to George Peter Staplin   
   Re: 32-bit vs. 64-bit x86 Speed   
   23 Apr 07 07:53:17   
   
   From: haberg@math.su.se   
      
    George Peter Staplin  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   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)   

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