On Nov 16, 2007 7:33 AM, David Leimbach <[EMAIL PROTECTED]> wrote: > > On Nov 16, 2007 6:46 AM, erik quanstrom <[EMAIL PROTECTED]> 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/
