x86_64

[Ed Hill]

On Tue, 2006-03-07 at 08:56 -0500, Jerry Feldman wrote:
> On Tuesday 07 March 2006 6:43 am, jbk wrote:
> > James Kramer wrote:
> > > Some questions I have and would appreciate some insight.  It seems to
> > > me that Xen type systems may become more common in the future.  If so,
> > > would 64 bit be a better option?  How much difference is there in
> > > converting software to 64 bit.  I realize that memory allocation would
> > > be different but is there much more work then recompiling the code?
> > > These are all questions--I don't know the answers.  I have converted
> > > some Fortran code from 64 bit mainframe to 16 bit PC and I really don't
> > > remember worrying about the number of bits.  How much more conversion
> > > is necessary.

Some code (C, C++, Fortran, and other languages) written for i386 is
"64-bit clean" and will work with just a recompile.  And some code
requires a bit of extra work to fix problems such as assumptions that
ints and pointers are the same size.

If you look at the software shipped in a current Linux distribution such
as Fedora, Mandriva, Debian, etc. you'll see that the binary packages
(RPMs and debs) are for the most part all built from the same (often
identical) sources.  In some cases, it was easy (trivial!) to build
these packages from the same source code on both 32bit and 64bit
platforms.  And it some cases it took a few little changes (eg.
multi-lib handling such as /usr/lib64 vs. /usr/lib).  And it some cases
it took a lot of hard work making patches and testing.

Luckily, the lots-of-hard-work case is less frequently encountered
because 64-bit systems are now quite common.

Ed

-- 
Edward H. Hill III, PhD
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