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Re: [Qemu-devel] [PATCH] Enabled building of x86_64 code on Mac OS X


From: Jamie Lokier
Subject: Re: [Qemu-devel] [PATCH] Enabled building of x86_64 code on Mac OS X
Date: Tue, 27 Jan 2009 00:42:32 +0000
User-agent: Mutt/1.5.13 (2006-08-11)

Paul Brook wrote:
> > Out of curiousity, what are the benefits of using 64-bit apps in OS X?
> 
> My guess is that same as most other x86 targets: The i386 legacy
> mode is crippled by lack of registers, modern x86 hardware has a big
> fat wide memory bus, and noone's bothered implementing an ILP32
> 64-bit API[1], so 64-bit apps give measurably better overall
> performance.

Except they use more memory and memory bandwidth (arguably filling
nearly half of it with zeros most of the time :-) so worse overall
performance in some cases.

-- Jamie




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