[LAU] OT: 64 vs 32 bit?

Goran Mekić meka at ns-linux.org
Mon Sep 27 22:20:37 UTC 2010

On Mon, 27 Sep 2010 10:57:46 -1000
Joel Roth <joelz at pobox.com> wrote:

> On Mon, Sep 27, 2010 at 10:30:12PM +0200, Fritz Meissner wrote:
> > On 27 September 2010 22:26, Josh Lawrence <hardbop200 at gmail.com> wrote:
> > > Hi everyone,
> > >
> > > I'm late to the party when it comes to 64-bit machines, so apologies
> > > in advance if I am asking something that should be obvious...
> > >
> > > I recently purchased a 64 bit machine and like it a lot, but I've
> > > noticed that some software that is usually available on a 32 bit
> > > machine isn't available in the 64 bit repos that I am using.  Can I
> > > install the 32 bit version of my distro (Debian) on my 64 bit machine?
> > >  I'm assuming that would give me access to all 32 bit software.  It
> > > would also be a performance hit, correct?
> > >
> > Yes, you can install the 32 bit version. From what I have heard, the
> > performance difference is not significant, but the major benefit of 64
> > bit is being able to address more than 4 GB of memory, which is the
> > limit of what a 32 bit OS can use.
> One advantage to 64-bit machines is that there are more
> CPU registers available in 64-bit mode, so some processing 
> goes faster, and more addressable memory.
> That may be reason enough to run a 64-bit kernel while
> keeping a 32-bit userland (libraries, applications, etc.)
> Which some (including myself) do.
> The advantage of 32-bit software is a smaller
> memory footprint (e.g. 32 bits to represent an 
> integer instead of 64). There is a much wider software
> availability, and fewer compatibility issues.
> Although many say "64-bit is well established, no need
> to worry about compatibility", I've had a few run ins.
> At one point, I was maintaining two parallel Debian systems,
> one 32-bit and one 64-bit, to track down such issues.
> Some disadvantages to mixed systems, from the amd64 faq
> at http://alioth.debian.org/docman/view.php/30192/21/debian-amd64-howto.html
>     Q: I want to run i386 userland with a 64bit Linux kernel
>     A: Running 32bit userland with a 64bit kernel is recommended
>     only for servers needing the absolute stability of 10 years
>     of 32bit debian, but without the memory limitations the IA32
>     architecture bears, for example a 64bit mysql server on a
>     system with 8GB or 16GB memory.
>     Running the mixed setup on a workstation is not recommended,
>     because iptables, the XFS filesystem, non-free NVidia and
>     ATI binary drivers do currently not support it. 
> Iptables *does* appear to work for me in mixed environment,
> at least the user interface part.
> Cheers,
> Joel
> > Fritz

	64 bit x86 architecture DOESN'T use 64 bit integers. For those of you that undestand the following code, try to compile a program that has int x = new int; That will warn you about asigning 64bit pointer to a 32bit integer (if it doesn't warn you about asigning pointer to non-pointer variable). Another thing, I use 64bit Gentoo, and do my share of audio production (recording demos of my band, nothing fancy). I haven't found any 32bit app that I miss so far (now that flash is working again). Can you tell us which 32bit programs you need?

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