amd64 slower than i386 on identical AMD 64 system?

Alexander Konovalenko kono at
Tue Mar 14 11:38:13 UTC 2006

On Tuesday 14 March 2006 11:40, JoaoBR wrote:
> so where is your comparism? My point was that the same hardware is faster
> running i386
> I experience this also on X2 machines but do not have two machines to
> compare I have a X2-4400-SMP running amd64 and a X2-4200-SMP running i386
> and it gives me the same numbers running ubench

I have experienced that -O3 and -ffast-math optimizations flags on AMD64 might 
cause degrade in performance, meaning that -O2 is the fastest. When you 
compile your ports what opt. flags do you use? Try to reinstall ubench with 
different flags. Also code produced with gcc4.x is faster then system 
compiler and has no degrade effect. Some time ago I was interested in fast 
scientific computations and did some primitive benchmark tests 

I just wonder what will happen if you run ubench (compiled for i386) on AMD64, 
will performance overcome amd64 ubench? 

/Alexander Konovalenko

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