Hadron wrote:
> Andrew Halliwell <spike1@ponder.sky.com> writes:
>
>> Aragorn <aragorn@chatfactory.invalid> wrote:
>>>> Are there any advantages and disadvantages between 686 and amd64 beside
>>>> being able to use more memory which I doubt I am going to (2 GB is
>>>> enough).
>>> Well, the /AMD64/ kernels are more likely to contain some processor-specific
>>> code optimizations than a generic /i686/ kernel,
>> There's a bit more to it than that....
>> x86-64 is more than just a wider address bus, it also contains a shedload
>> more cpu instructions, such as SSE3, iirc. There're also a lot more
>> registers available in 64bit mode. Which means less fetching from RAM during
>> calculations.
>>
>> These enhancements may (in some situations) make it faster...
>> But I think the general consensus is, speed is generally slightly slower
>> because 64 bit applications tend to be slightly bigger due to the extended
>> instruction set and data-width taking more memory/disk space.
>
> This was hotly contested by some in comp.os.linux.advocacy but is
> effectively correct. I saw no speed improvement in 64 bit over 32 bit
> and just suffered from a far less stable system.
>
>> If you don't need more than 4gig of RAM, chances are, you're fine in 32 bit
>> mode, and may even be slightly better off, performance wise.
>
> And certain things like flash do not work properly.
>
> See:
>
> http://groups.google.com/group/comp....5d987c45c9499c
>
> It is however getting better.
>

I think this is largely correct: I had this choice to make..for a
moderately loaded server.

Looking at some of the problems associated with the 64 bit kernels, and
realizing that by and large my actual applications were not hugely
computationally intensive, but more disk I/O bound, there seemed little
point in taking the small risk of a 64 bit kernel and libraries.

If I were building a massive server to handle many processes, then yes,
4gig RAM plus, and a 64 bit kernel would be indicated.

Or a desktop to do graphics work.