F 15. 64 bit versus 32 bit.

[Misha Shnurapet]

25.05.2011, 21:13, "Andrew Haley" <aph at redhat.com>:
> On 05/25/2011 12:58 PM, Bill Davidsen wrote:
>
>>  Chris Adams wrote:
>>>  Once upon a time, Fernando Cassia<fcassia at gmail.com>;  said:
>>>>  Well guess what? 64 bit code is bigger (bigger pointers) and thus
>>>>  slower, because CPU cache is less effective, with bigger code.
>>>  All other things being equal, that might be true.  However, all other
>>>  things are NOT equal; pointer size is not the only different between
>>>  i686 and x86_64.  The biggest gain is that x86_64 has a much larger
>>>  register set, so a lot of things don't have to hit RAM at all (and are
>>>>  much faster).
>
> Also, the ABI is much better, and this may be almost as significant.
>
>>  Unfortunately that biggest gain only occurs if the program logic is such that
>>  registers run out often.
>
> Which, in the case of gcc-generated code, is most of the time.  gcc
> was originally written for, and still works best with, a machine with
> 16 or more general-purpose registers.  32- bit x86 only has five or
> six registers to play with, and this just isn't enough for good code
> generation.  I don't think that Java has it very much easier.

I have been running x86_64 since Fedora 10, but had issues with 3rd party games that refused to run (with all the 32-bit libraries in place). So, going for all-32-bit with Fedora 15.

I have 2 gigs of RAM. With more than 4 gigs the x86_64 is the only to go.

-- 
Best regards,
Misha Shnurapet, Fedora Project Contributor
https://fedoraproject.org/wiki/Shnurapet
shnurapet AT fedoraproject.org, GPG: 00217306