This isn't an exact comparison, CPU speed for CPU speed, but I recently upgrade to an Intel 4300 which I overclock to 2.88GHz with DDR2 800 memory. My old rig was an Opty 165 running at 2.5 GHz with DDR 400 memory. I did a test with DVD Shrink, using the exact same files and exact same quality settings. The Intel C2D did the encode in 25 minutes. The Opty did the same exact encode in 45 minutes. To me this isn't just a meaningless benchmark, this is a very real, measurable performance gain for encoding, which plenty of people do with their computers.
Some of this can be attributed to the slower clock of the Opty, 2.5 vs. 2.88, and some of it can be attributed to the slower memory, 400 vs. 800, but the end result in my test was the C2D smoked the Opty. I mean it smoked it! Rarely have I done an upgrade where a simple test like this was so dramatically faster than the previous one.
Some of this can be attributed to the slower clock of the Opty, 2.5 vs. 2.88, and some of it can be attributed to the slower memory, 400 vs. 800, but the end result in my test was the C2D smoked the Opty. I mean it smoked it! Rarely have I done an upgrade where a simple test like this was so dramatically faster than the previous one.