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32- and 64-bit performance
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Date: -- (:)
From: Ville-Pertti Keinonen <will@e...>
Subject: Re: [Caml-list] 32- and 64-bit performance
On Wed, 2005-03-30 at 09:46 +0200, Alex Baretta wrote:

> Why do you suppose is there *any* benchmark faster in 32 bit mode than 
> in 64 bit mode on the Athlon64? Since the AMD64 architecture is 
> generally better than IA32--were it only for the additional registers--I 
> would expect all benchmarks to run as fast or faster when compiled to 
> the AMD64 instruction set.

64-bit data structures (due to bigger pointers, alignment, and in OCaml
bigger default integers) are bigger, so things that are constrained by
memory bandwidth are obviously going to be faster as 32-bit.

On other architectures where you can use 32-bit or 64-bit that are
otherwise identical, 32-bit is generally faster.