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Re: Confusion about 32/64-bit user space

On Tue, Aug 20, 2002 at 02:28:21AM -0400, Scott Robert Ladd wrote:
> I am a tad confused here, so bear with me...
> Okay: I have an Ultra 10, on which I've installed Debian 3.0r0. As I
> understand it, the kernel operates in 64-bit mode, while any programs I
> write and run operate in 32-bit mode. Is that correct?
> Is there anyway to change user space such that it is 64-bit?
> This came up when I built gcc 3.2; the configure script couldn't figure out
> my installation. As it is explained to me by someone in the gcc mailing
> list, what I managed to build was a 32-bit version of the compilers, given
> that my user space is 32-bit.
> Why isn't user space 64-bit by default? Is it that many GNU/Linux programs
> aren't compatible with 64-bit?

You don't want 64bit userspace is very very slow compared to 32bit. The
only reason you would want 64bit binaries is if a single program needs
to access > 4gigs of memory (note, this has nothing to do with just
having > 4gigs of memory).

Most programs are compatible with 64bit userspace (hence ia64 and alpha
actually working), but that doesn't mean it's appropriate for normal use
on a machine that can handle 32bit natively.

Debian     - http://www.debian.org/
Linux 1394 - http://linux1394.sourceforge.net/
Subversion - http://subversion.tigris.org/
Deqo       - http://www.deqo.com/

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