How Many CPU Cores Do You Need?

A few months ago, we looked into the effectiveness of using different numbers of CPU cores with various types of software. We received a lot of good feedback from that article, and there were some interesting suggestions from the community that we've taken to heart in this follow-up.

Primarily, there was a concern that part one might have been flawed technically, as the Core 2 Quad Q6600 we used in our testing does not share all 8 MB of its L2 cache between its four CPU cores. Intel's Q6600 instead has two separate 4 MB cache repositories, each shared between one pair of CPU cores. This means the quad- and triple-core results would have demonstrated the CPUs utilizing 8 MB of total cache, while the dual- and single-core results show that they were likely benefiting from 4 MB. Indeed, the benchmarks may have been reflecting the difference in L2 cache availability more than performance attributable to enabled processing cores.