According to Intel's product brief, the 4MB L2 cache of a Woodcrest processor is shared, not discrete.
I believe this is where the performance advantage comes from, access to 4MB of L2 cache.
product brief
"4 MB shared L2 cache
• Entire L2 cache can be allocated to one core."
From the
Folding@home SMP FAQ
"Before releasing any new project (series of work units), we benchmark it on a dedicated Macintosh Pro with 2 - 2.33 GHz Dual Core Xeon processors. (more specifically, 2 Woodcrest 5140 processors with 4 MB cache (each), 5 GB FBDIMM Memory (667 MHz DDR2), 1.33 GHz Bus)"