NVIDIA’s Project Kal-El processor implements a novel new Variable Symmetric Multiprocessing (vSMP) technology. Not previously disclosed publicly, vSMP includes a fifth CPU core (the “Companion” core) built using a special low power silicon process that executes tasks at low frequency for active standby mode, music playback, and even video playback. The four main “quad” cores are built using a standard silicon process to reach higher frequencies, while consuming lower power than dual core solutions for many tasks. All five CPU cores are identical ARM Cortex A9 CPUs, and are individually enabled and disabled (via aggressive power gating) based on the work load. The “Companion” core is OS transparent, unlike current Asynchronous SMP architectures, meaning the OS and applications are not aware of this core, but automatically take advantage of it.
"Aggressive power gating" ... I love it!
There's more information available from the links in the NVIDIA blog.