Re: Why the 64 bit ISA is better
Stan Hoeppner <stan@hardwarefreak.com> writes:
> Given the recent threads regarding 32 vs 64 bit I thought I'd take a
> moment to present information often omitted in responses to these posts.
>
> [ some good explanations ]
Another often underestimated bit is the new addressing mode relative
to the instruction pointer %rip. This greatly reduces the performance
overhead of position independent code needed for shared libs.
On the other hand, the penalties that come with 64 bit are also often
underestimated: Pointers are 64 bit wide and this can increase memory
foot print considerably. Argueing with decreasing costs for main
memory neglects the fact that even this larger memory must be
inited/loaded from disk, transferred to/from CPU thru the memory bus
and pointers also require more space in CPU cache memory which cannot
easily be enlarged.
Nevertheless, I always prefer the amd64 installation instead of i386
when installing on new machines.
urs
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