That big of a difference in speed, by a factor of 4 or 6, feels like it's likely to be some quirky weak spot or instruction that the old chip is slow with. Unless it's a touted feature of the i5 that they made SSE2 six times faster. A quick summary: Xeon Quad 41% slower Core 2 Duo 55% slower Core 2 Duo same (vess) Core 2 Quad 50% slower Core i5 200% faster (nelisky) Core i5 100% faster (vess) AMD Opteron 105% faster aceat64: My system went from ~7100 to ~4200. This particular system has dual Intel Xeon Quad-Core CPUs (E5335) @ 2.00GHz. impossible7: on an Intel Core 2 Duo T7300 running x86_64 linux it was 55% slower compared to the stock version (r121) nelisky: My Core2Quad (Q6600) slowed down 50%, my i5 improved ~200%, impossible7: on an AMD Opteron 2374 HE running x86_64 linux I got a 105% improvement (!)
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