8-Core (Clovertown) Mac Pro Benchmarks
The quad-core Xeon 5300 (Clowertown) represents a pin-compatible replacement for the current dual-core Xeon 5160 (Woodcrest) processors that currently reside in the Mac Pro. This possibility was previously demonstrated by AnandTech when they successfully dropped Clovertown samples into the current Mac Pro. No benchmarks were available at that time, but CNet has now posted benchmarks of this same configuration:
As the Xeon 5355 is pin-compatible with the Xeon 5160 processors that came installed in our Mac Pro, we proceeded to swap out the two dual-core processors with the new quad-core processors. .... With the pair of Xeon 5355 processors installed, we booted the system back up and were greeted with eight active processing cores in both the Mac OS and Windows XP via the Boot Camp Public Beta.
Benchmarks compared 3.0GHz 4-core Mac Pros (Woodcrest) vs 2.66GHz 8-core Mac Pros (Clovertown) and showed a 31% improvement in highly multithreaded benchmarks such as Cinebench. iTunes and Quake saw less significant improvements. Their conclusion was that "unless you do work normally relegated to high-end workstations, perform massively multitasking workloads, or just want the bragging rights, eight cores is definitely overkill...at least for now."
Apple had been rumored to be introducing 8-Core Mac Pros as early as this month.