RS: [Beowulf] Sempron compile optimization
lindahl at pathscale.com
Mon Nov 28 21:20:24 PST 2005
On Tue, Nov 29, 2005 at 03:40:04PM +1100, Chris Samuel wrote:
> Don't get me wrong, I've been able to build 64-bit versions of NAMD and
> various other codes on SLES9 on PPC64 successfully, but I am suprised that
> it's not fully native 64-bit. I certainly was under the impression it was.
That depends on what "native" means. SGI shipped 64-bit OSes where
most of the binaries were 32-bit. The only reason Opteron OSes are
64-bit is because of the extra registers in 64-bit mode, meaning that
most programs are faster as 64-bit programs. Our compiler is a 32-bit
app because it uess a lot of pointers, and so the speed hit of fewer
registers is more than made up with less cache busting.
Both gcc and our compiler really support 64-bit compilation from a
32-bit compiler executable, so it's not actually "cross compiling".
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