You’d be forgiven for finding that headline slightly confusing. Yes: quad means four, and yes: Nvidia’s quad-core Kal-El chip has five cores. There is logic to the madness, fear not.
The cheeky fifth chap is called a “companion core”, and is used “primarily when the mobile device is in active standby and performing background tasks.” Interesting.
In a whitepaper called Variable SMP – A Multi-Core CPU Architecture for Low Power and High Performance (catchy, huh?), Nvidia explains how the surprise fifth core is implemented:
“Not previously disclosed publicly, Variable Symmetric Multiprocessing 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.” Excellent. Improved battery life, then?
The paper continues: “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.”
Good stuff. And here we were thinking we’d need to charge our quad-core superbeasts twice daily.