Here:
http://www.eweek.com/article2/0,1759,2114747,00.asp
At the April 17 conference in Beijing, company officials went a step further and disclosed new performance specifications. For example, a Penryn processor with a 1600MHz FSB (front side bus) in a workstation or Penryn processor with a 1300MHz FSB in a server will offer 45 percent better performance for bandwidth-intensive applications and 25 percent greater performance for a server using Java. In this scenario, Intel compared the two pre-production processors with a quad-core Xeon 5355 processor.
Intel also compared a Penryn processor with a clock speed of 3.3GHz, a 1333MHz FSB and 12MB of Level 2 cache with its quad-core Core 2 Extreme QX6800, which the company just released on April 9. The results showed a 25 percent greater performance with three-dimensional rendering, a 40 percent increase in gaming performance and a 40 percent increase in video encoding.
[I think that the massive 12 MB cache and whatever access sharing scheme Intel has implemented is contributing to this performance as it doesn't seem to be *so* dependant on the FSB speed.]