32bit or 64bit?

[Marek Podmaka <marki@marki-online.net>]

Hello all,

I just yesterday learned that my Xeons are in fact 64bit, so I have
few questions about it...

1) What is the performance gain between running 32bit and 64bit linux
on 64bit capable CPU? I'm running Etch with apache+php+mysql. Is it
worth upgrading?

2) Performance is gained just by compiling the same source code into
64bit binary? Or are the main apps (apache/php/mysql) optimized in
source code to benefit explicitly from 64bit?

2) Is it possible to run 64bit kernel, but 32bit
application/libraries/everything? (So just recompiling kernel). If
possible, is it better than 32bit kernel + 32bit apps?

3) Is it somehow possible to upgrade the 32bit debian into 64bit?
Preferably with as little downtime as possible...

   many thanks :)

-- 
  bYE, Marki