AMD Athlon64 Systems

[Mike A. Harris]

On Sat, 18 Oct 2003, Jakub Jelinek wrote:

>> >> What is the 32/64 bit split in Sparc linux distros? PowerPC distros?
>> >
>> >Aurora is 64-bit kernel, 32-bit userspace on UltraSparc
>> 
>> AMD64 architecture provides more benefits to general 64bit apps 
>> than broken 64bit sparc processors do.  ;o)
>
>Dunno why you said this is broken (on the contrary IMHO).
>If there was a 32-bit AMD64 ABI using the additional
>registers, parameter passing in registers, %rip addressing etc.,
>such code would certainly outperform AMD64 64-bit code,
>simply because 64-bit apps have necessarily bigger cache footprint,
>and as long as the application doesn't spend a lot of time doing
>long long arithmetics or needs really big virtual address space,
>there should be no reason to go for 64-bit apps.

Your argument is entirely hypothetical however.  I've not seen 
any proof that the increased cache footprint makes much of a 
difference personally.  Speaking in terms of what exists today 
here and now - AMD64 64bit OS and userland apps outperform x86 
32bit OS running on the same machine hands down.

If anyone has information to the contrary however, I'm definitely
open eared and eyed to have a look at their non-hypothetical test
results.  ;o)



-- 
Mike A. Harris     ftp://people.redhat.com/mharris
OS Systems Engineer - XFree86 maintainer - Red Hat