The NVIDIA Tegra 4 processor equipping the NVIDIA Shield tablet offers several modes of operation, namely:
-The max performance mode (gaming mode)
-The optimized - a balanced mode.
-The power saving mode - a configurable battery saving mode.
Indeed, when using your tablet for basic tasks (listening to music, browse the internet,... ) you can switch to the optimized or power saving mode.
Here's how to customize the Processor mode: