Benchmark Results: iTunes 10.6.1
iTunes is single-threaded, so it reflects the performance of each CPU running at its highest Turbo Boost/Turbo Core clock rate. The Ivy Bridge-based Core i7-3720QM enjoys a raw frequency advantage and better instruction-per-cycle throughput, putting it in the lead. The other two Intel chips follow closely behind. Despite a peak 2.6 GHz Turbo Core clock rate, AMD's A8 simply cannot keep up.
With up to one core utilized at any given time, a workload like this is generally going to look pretty light (though it's interesting that AMD's chip gets as high as 50%).
Although the Ivy Bridge-based Core i7-3720QM only spins up a single core, it pushes that piece of logic to 3.6 GHz, exploiting as much available TDP as possible. Core i7-2820QM, manufactured at 32 nm, only hits 3.4 GHz, but it's not as efficient, so power consumption spikes slightly higher.
Pushing one-fourth of a quad-core chip with a 45 W TDP translates into modest power use. It's almost counter-intuitive that the 35 W Core i5 would use even more energy. However, remember that our Arrandale sample is a dual-core model, so we're monopolizing half of its on-die resources to do the same task.
As we've come to expect, AMD's A8 maintains very low power use, but over a painfully long period of time, negating any benefit the APU might have seen from its sub-20 W figure.