AMD Athlon64 Systems

Jakub Jelinek jakub at redhat.com
Sat Oct 18 11:09:57 UTC 2003


On Sat, Oct 18, 2003 at 05:41:46AM -0400, Mike A. Harris wrote:
> On Fri, 17 Oct 2003, Chris Ricker wrote:
> 
> >> Does a 64bit mozilla even make sense right now?
> >> I'd think just using the 32bit version would be fine. And no issues with 
> >> plugins.
> >
> >yep -- for most apps, going 64-bit is pointless
> 
> Depends on the specific CPU architecture.  For AMD64, 64bit means 
> that you also get a slew of additional registers for gcc to use 
> for optimization for free.  In my experience 64bit applications 
> have a definite benefit over 32bit on AMD64, the exception being 
> apps that are highly disk or network bound (I/O bound), which 
> don't benefit much.
> 
> 
> >> 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.

	Jakub





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