Conclusion
Our testing reveals that many workloads are still very much incapable of taking advantage of more than two cores. Titles like WinZip have not yet been optimized to run more than one thread, and it's a shame. Even the cheapest dual-core processors could deliver much better performance, if only the software would support it. This not only applies to the Lame MP3 encoder, but also to Apple’s iTunes and Adobe’s Acrobat 9, which is used for creating PDF documents. Since Apple and Adobe aren’t exactly nobodies, this fact disappoints even more.
But let’s get back to our scaling analysis. Switching off processing cores will not reduce system idle power. AMD did a great job of mastering its power management on the 45 nm Thuban core. The system runs within the same 81W to 83W whether one or six cores are used. However, the results in peak power consumption show that average power draw per core drops with additional cores. In the end, peak power doesn’t differ much whether four, five, or six cores are active. Yet, performance still increases considerably under thread-optimized workloads.
For this reason, AMD’s Phenom II X6 offers great performance, thanks to six processing cores, as well as increased efficiency as you scale up core count. Clearly, utilizing as many cores as possible maximizes performance per watt power efficiency. In other words, given that idle power doesn’t change, and both performance and power efficiency increase with the core count, it doesn't make sense to switch off cores manually.
