With both my new.built Xeon-1240/EVGA660 and legacy AMD965/EVGA650 systems smoothly running U_12.04 @ a nominal 3.4GHz. I'm tempted to run A/B speed tests using the Phoronix test suite.
Not being a gamr and not currently running computational science projects (my WinXP Celeron sys gets to do that!) such speed tests are a small amusment ... and frankly a surprise as the legacy AMD965 system certainly holds its own! The latest test focused on cpu function, expecting the 8-thread XEON + 24-GIG (1333) ram to walk-all-over the plucky-but-outclassed legacy AMD965 w/12-GIG (1066) :
Very respectable not-to-say shocking desktop performance by the legacy hardware. Now hardcore gamrz or a WallStreet trading whiz will poopoo the comparison ... and perhaps even the hardware. I had fun and learned lots (much from THW gurus) building and cajoling both systems. But, considering there's five (5) years of development and (say) $15-B in research costs separating the two sets of components a reasonable man might well ask ---- what have I bought ??
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I don't know if it's respectable performance, 6.6 vs 3.3, that's a 100% performance gain. This is only one benchmark tool as well. Try a RAM benchmark, you should see a significant improvement.