Using asymmetric cores to reduce power consumption for interactive devices with bi-stable displays

Low power “helper ” cores have been increasingly included on application processors to accomplish low intensity tasks such as music playing and motion sensing with minimum energy consumption. Recently, Guimbretière et al. [1] demonstrated that such helper cores could also be used to execute simple user interface tasks. We revisit this ap-proach by implementing a similar system on an off-the-shelf application processor (TI OMAP4). Our study shows that in the case of high event rate interactions (pen inking and virtual keyboard), significant battery life gains (×1.7 and ×2.3 respectively) can be achieved with the helper core executing the interface. Having the helper core only dis-patch input events incurs a 18 % penalty relative to the max-imum savings rate, but allows for simplified deployment since it merely requires a change in toolkit infrastructure