From: Scott L. B. <Sc...@sy...> - 2007-07-24 16:43:05
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On Jul 24, 2007, at 7:57 AM, Martin Cracauer wrote: > Scott L. Burson wrote on Fri, Jul 13, 2007 at 11:27:46AM -0700: >> Also, the recent Intel chips (including the 5160) have performance >> optimizations in 32-bit mode that are not active in 64-bit mode. So >> even with a compiler that makes good use of extra registers, the >> speedup normally seen in going from 32- to 64-bit mode is smaller >> than it would be on the AMD chips. > > Can you point me to more concrete information on the 32-bit only > optimizations in Core2? I have heard about these ever since the first > samples of Conroe were floating around. My own testing did indicate > that this is not the case. I saw the same speedup of Core2 over AMD64 > in 32 code and in 64 bit code, within single percent. An interesting result. I stand corrected. I was only repeating what I had read. Nathan's example of CMP/JMP macro-fusion is the optimization I recall also. Which compiler were you using? -- Scott |