13. Battery Lifetime

As the first set of measurements shows, the Intel system consumes about seventeen percent less energy under these circumstances. Because both systems used DDR RAM, it's safe to assume that the Turion 64's battery life suffers because the entire L2 cache remains permanently active during runtime. At 2 MB, the Pentium M's L2 cache is twice as big at the Turion 64's. But the Pentium M also uses a form of "intelligent switching" as well, so that only 1/64 of the entire cache remains active permanently, and consumes power at all times.

During DVD playback the optical drive and the graphics subsystem both consume energy, and the system cooler also comes into play as another power drain, though the CPUs only poke along at minimal core clock rates. Under these circumstances, the W511A openly displays a worse energy budget than does the M635 Turion 64 system. In fact, the Turion 64 device enjoys as much as 10 percent longer battery life than does the Intel platform in this situation.

During game-play the 3-D components of the graphics subsystem and the video RAM consume the lion's share of battery power. Because the CPUs also run at max rates throughout the test, the intelligent switching in the Pentium M's L2 cache confers no measurable advantage in this situation. Because of its small L2 cache and its slower core clock rate the Sempron emerges as the best performer in this scenario. In addition, the graphics components receive less of a workout from the Mobile Sempron. But all enjoyment of the Sempron's longer battery life must be tempered with the realization that 3D performance also suffers noticeably as well.

The table-based presentation of the relationships between Thermal Design Power of the CPUs, battery capacity and average power consumption for our three application scenarios show how much energy each of the three test platforms consumes for each usage model, and most importantly, which of them is the most power-hungry.