Re: [Mactel-linux-users] benefits of 64bit [was: Debian on MacBook2 installation report]

[Miguel S. F. <mig...@gm...>]

Hi,

On 12/20/06, mike dentifrice <fl...@po...> wrote:
> Tino Keitel said:
> > Newer MacBooks have a Core 2 Duo instead of a Core Duo CPU. As all
> > Core 2 Duo CPUs have EM64T, those newer MacBooks have EM64T, too
>
> Talking about that, what about the actual gains of using a MacBook2 with
> a native 64 bits environment, over the classical 32 bits system?
>
> Especially after reading wikipedia's "32 vs 64 bit" [1] and "pros &
> cons" [2] entries, it doesn't seem like a 64 bit userland brings any
> revolution to the desktop user.
>
> I'd be interested in hearing experiences, possibly by people who've
> tried both 32 and 64 bit distributions on their Code 2 Duo machine,
> noticed or measured differences.


I've ran 32 and 64 bit aplications on x86-64 machines.
The performance diferences are noticeable only in small cases:
- criptography and some types of maths can be quite faster on 64bit
versions. (64bit registers for operating doubles, and other sutff).
(there can be worse performance on aplications that are very fine
tuned to use vector instruction on x86, but do not have the same
tuning for x86_64 versions).
- ability to use more than 2/3/4gb for aplication virtual memory
(default limit on linux/x86 is 3gb for aplication virtual memory).

"funcionality diference"
- having non-exec stack by default (linux.. on x86_64)
- 64bit apps can also have a somewhat bigger memory footprint.
(pointers are bigger, so are assembly instructions/parameters)

other (and more plausible diferences)
- aplications that will non compile/run correctly on x86_64 (wrong
assumtions on  the pointer size - for instance)
- inability to have flash working with a x86_64 firefox.  - basically
there are problems with linking and mixing 64bit apps with 32bit libs,
and vice-versa.  That can be even more problematic in "binary only"
apps.

>
> Thanks in advance!
>
> [1] http://en.wikipedia.org/wiki/64_bit#32_vs_64_bit
> [2] http://en.wikipedia.org/wiki/64_bit#Pros_and_cons
>
> --
> mike dentifrice <fl...@po...>
>
>
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-- 
Miguel Sousa Filipe