Re: [9fans] Current status of amd64 port?

["David Leimbach" <leimy2k@gmail.com>]

On Nov 16, 2007 7:33 AM, David Leimbach <leimy2k@gmail.com> wrote:
>
> On Nov 16, 2007 6:46 AM, erik quanstrom <quanstro@coraid.com> wrote:
> > > Per your second a), performance does often improve quite a bit with 2x
> > > the general purpose registers.
> > >
> >
> > do you have some specific numbers to back up this claim?
> >
> > - erik
> >
>
> Not handy, but I used to build MPI applications on Opterons in 32bit
> mode, then build them in 64bit mode, and nearly always get a
> performance boost out of the 64bit.  Which was the exact opposite that
> I'd get on PPC 32 vs 64 bit.
>
> PPC's a different animal, using 32bit instructions even when in a
> "64bit mode" (doesn't really have modes), some immediate memory loads
> can use up to 5 instructions in assembly... I didn't look much deeper
> than that.
>
> I know I'm not alone in this observation either.
>
> I'm sure I could google some results, but I can't currently produce
> any of my own (unless I can get some time to do so on Leopard, since
> it supports both).
>
> Dave
>

http://www.geekpatrol.ca/2006/09/32-bit-vs-64-bit-performance/