Re: [gentoo-amd64] Can I run a 32-bit kernel on my 64-bit kernel Gentoo machine?

[Matt Randolph]

Mark Knecht wrote:

>   So, to check how this hardware platform works in a 32-bit mode I
>guess I need to do a complete second install on a separate part of the
>hard drive as an Athlon. That's a big job that I'm not anxious to do.
>
>Cheers,
>Mark
>
>
>

If you're just trying to compare the performance of your software 
between 32-bit and 64-bit kernels, you might try a distro that installs 
more quickly.  If I recall, you can install a complete 32-bit Debian 
system in about half an hour using a Knoppix CD.  Google `knoppix 
"install to hard disk"` for the howto.  I believe you can also get a 
64-bit Debian system just as quickly for comparison by following the 
same procedure but using a Kanotix-64 CD instead.  (You might just 
compare against your existing 64-bit Gentoo system instead, but I don't 
know how fair a fight would be between a hand-tuned Gentoo system and 
one running a binary distro.)

The only hitch I can think of is that some of your applications might 
not be available as Debian binaries in both 32 and 64-bit versions.  
Also, naturally, you won't have the ability to test your software with 
the optimizations afforded by the USE flags you intend to use back here 
in Gentoo-land.  If you would be building your software from source 
anyway, then this would not be an issue.

That being said, I think this experiment would actually be pretty 
academic for most users.  Unless your software is, say, a very CPU 
intensive scientific or multimedia application that was expertly ported 
to 64-bit, it is my understanding that you're probably not going to see 
a performance difference worth writing home about.  I would encourage 
anyone to comment if they know better as I would be delighted to learn 
it was otherwise.

- Matt

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