[aklug] Re: 32 vs 64 bit

On Fri, Oct 22, 2010 at 04:33:16PM +0800, Bruce Hill wrote:
> On Fri, Oct 22, 2010 at 03:23:56AM -0400, Christopher Howard wrote:
> > On Thu, Oct 21, 2010 at 05:16:42PM -0700, James Tweet wrote:
> > > I just got a laptop that has a 64-bit processor. On it I put the 64 bit version
> > > of Ubuntu and I want some info on peoples experiences.
> > >
> > > Questions:
> > > Are there any major differences between the 32 and 64 bit programs?
> > > Are there any gotchas that I should look out for?
> > > If I ran the 32-bit version of Ubuntu would it run slower, faster or the same?
> > > If I run 32-bit software on the 64-bit OS will it effect performance?
> > > Can I just recompile 32-bit code into 64-bit code?
> > > Any other advice or observations?
> > >
> > > Thanks
> > > James
> > >
> >
> > This is not my special area of study. From what I understand, however, there should be measurable performance improvements by virtue of switching to a 64-bit OS, on account of the fact that the x86-64 extension provides access to eight additional cpu registers, which allows the code to keep more operational data off of the stack and on the faster registers.
> >
> > Running 32-bit software on 64-bit OS should not have any negative impact on performance (aside from the inherent limitations of the 32-bit code) because x86-64 is fully backwards compatible with x86.
>
> Unless you use benchmark software, such as bonnie++, I have serious doubts
> that you will notice the difference (assuming you're still running
> Gentoo). On an Athlon64 X2 5000+ with 2G RAM, and a Core2Duo T8300 @ 2.4GHz
> with 2G RAM, there is not a noticable difference.

Well, frankly, what minor code performance improvements are ever going to be "noticed" on Desktop machine, where the really bothersome delays typically related to io bottlenecks (disk io, bus speed, cache size, etc.) That, however, doesn't mean the performance improvements do not exist or are not beneficial. If encrypted blocks can be processed faster, gzip compression takes less time, or vlc becomes less resource intensive, this is ultimately going to help your productivity.

>
> Where there is a difference is when you want to run 32-bit apps, such as
> Skype, QQ, Wine, etc in a 64-bit OS. You need multilibs rather than a
> purelib 64-bit system, and the apps don't work the same as on their native
> arch.
>
> Just my 2c ... now running 32-bit OS happily.

And I've been running 64-bit OS's happily, for several years now. In my mind, 32-bit processors (along with single core chips) are legacy technology. We should encourage development of more powerful 64-bit software by running operating systems that actually are capable of running them.

-- 
Christopher Howard
frigidcode.com
theologia.indicium.us
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