Re: Transitioning to 64bit, is it worth it, and how
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On 08/04/07 14:31, Andrew J. Barr wrote:
> On 8/4/07, Ron Johnson <ron.l.johnson@cox.net> wrote:
>> On 08/04/07 12:53, Andrew J. Barr wrote:
>>>> a) What are the pros and cons in switching to 64 bit mode?
>>>> - Is it faster?
>>> Yes. Unlike true 64-bit architectures like PowerPC, there is a penalty
>>> for executing 32 bit code on amd64/em64t processors.
>> Penalty? Absolutely fscking not!!!! The A64 processes 32 bit code
>> at a similar speed to "regular" Athlon CPUs.
>
> Do you have any sources for this? I remember quite distinctly seeing
> on a mailing list, I think it was debian-powerpc in fact, that the
> only reason that AMD64 operating systems have an all-64-bit user land
> is because there is a penalty for executing 32-bit code, one which is
> not present on other true 64-bit architectures. 64-bit code /does/ use
> more memory, so it is advantageous to have a mixed userland if you can
> afford it--e.g. only compiling applications that will benefit from
> 64-bit into 64-bit executables. This is what the OSes for other 64-bit
> architectures do.
>
> Perhaps the penalty is only under a 64-bit kernel...
I think we might have different definitions of "penalty".
What I mean is that an AMD64 in 32-bit mode will run apps at the
same speed as an equivalently-clocked AthlonXP.
- --
Ron Johnson, Jr.
Jefferson LA USA
Give a man a fish, and he eats for a day.
Hit him with a fish, and he goes away for good!
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