[aklug] Re: 32 vs 64 bit

From: Bruce Hill <bruce@slackwarebox.com>
Date: Fri Oct 22 2010 - 00:33:16 AKDT

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.

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.

-- 
May the Lamb that was slain receive the reward of His suffering!
"Experience is a hard teacher because she gives the test first, the
lesson afterward. But properly learned, the lesson forever changes
the man."
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Received on Fri Oct 22 00:33:31 2010

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