Hi,
On Mon, 15 Dec 2003, 6:14pm -0500, [log in to unmask] wrote:
> Toon Moene wrote:
> > Extra integer registers to hold array offset addresses
> Let me ask another question: Is there a reason to keep a program in 32-bit
> mode if it can be ported easily to 64-bit mode (i.e. assume it is portable,
> as Richard's)?
For SGI and AIX, 32-bit mode will run faster. I can accept that
this might not be true of Opteron, since more registers are available
in 64-bit mode.
For Opteron, if you are a commercial software provider, one fewer
platform to port to, QA regularly and deliver sure makes a
big difference. It would take at least a 25% performance increase
to make this even worth considering.
-P.
> My programs are usually FLOP or memory bandwidth bound and do
> not really need 64 bit integers (but all the reals are 64 bits). As I am
> reading, the reason behind the 32-bit mode is for backward compatibility and
> ease of migration, and the real thing to do is run in 64-bit mode once you
> port the code successfully.
> Any suggestions for reading on the subject?
> Thanks,
> Aleks
>
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