[Beowulf] Athlon64 / Opteron test

[Donald Becker]

[[ The mailing list should now be back up and running for all
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On Fri, 14 May 2004, Greg Lindahl wrote:

> On Fri, May 14, 2004 at 11:49:34AM -0400, Robert G. Brown wrote:
>
> > rgb at s02|B:1003>./Ospin
> > -bash: ./Ospin: /lib/ld-linux.so.2: bad ELF interpreter: No such file or directory
> > rgb at s02|B:1004>
> 
> Pilot error. You have to install a couple of additional rpms to run
> 32-bit stuff on an Opteron. The annoying thing about it is that they
> have the same names as x86_64 packages, grrrr. In this case you need
> glibc-*.i686.rpm.

That makes it sound easier than it really is...

We distribute 32 bit library RPMs with the Scyld Beowulf for AMD64
distribution.  But those libraries are not just a simple duplication of
the x86 32 bit RPMs.

The 32 bit library RPMs must contain only the libraries, not other
configuration and documentation files.  The libraries must placed
in the proper directories or otherwise made to have non-conflicting
names.  Some libraries that exist only as 32 bit versions must be placed
in the LSB-standard location.  And all of this get extra complicated
with 3rd party compilers.

We started out with an ad hoc approach, using the 32 bit RPMs, but
quickly decided that it had too many exceptions to support for end users.

> > ...it also refers to anecdotal accounts that numerical performance
> > significantly degrades if one runs i386 code compared to recompiled
> > x86_64 code.
> ...I don't think that you'd come to that conclusion. It is an apples to
> oranges comparison

There were list postings in March that pointed to cases where the 64 bit
instruction set was more compact and efficient than x86 32 bit native
mode, thanks largely to more general purpose registers.  The only part
that was surprising was the "more compact" part.


-- 
Donald Becker				becker at scyld.com
Scyld Software	 			Scyld Beowulf cluster systems
914 Bay Ridge Road, Suite 220		www.scyld.com
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