32bit Vs 64bit OS

[Kwan Lowe]

On Thu, Jun 17, 2010 at 9:28 PM, Monty wig <montywig at gmail.com> wrote:
> Hi Gurus,
>
> Can someone please point me the right direction on the difference between
> 32bit and 64bit OS?

For almost all situations, I don't see any benefit to staying with
32-bit on servers. There's apparently a narrow case for 32-bit on the
desktop for some specific applications, but my laptop is 64-bit.

As mentioned, the main advantage of 64-bit is address space. You can
access a heckuva lot more memory without tricks than you can with
32-bit. Keep in mind that this is *per process* memory also. With a
32-bit PAE kernel, the OS can access 64G (or thereabouts, I forget the
exact  number) but each process is still limited to 3G.  The PAE
kernel is/was necessary for certain legacy applications. With 64-bits
you don't have this limitation.

The areas where 64-bit apps is not a good idea is on some
applications, in particular Java-based apps. This hopefully will
change, but running a 64-bit JVM will require lots more memory and
even code changes because of how Java manages heap/memory. The common
practice is to run 32-bit JVMs on top of a 64-bit OS. But to repeat,
this is regarding the application rather than the kernel.