We’ve been deceived ! All along we thought the new quad-core Nvidia Tegra 3 (codename Kal-El) would just have 4 cores…right… But Nvidia has just posted a blog entry talking about a mysterious fifth core. There is also the 12-core GPU, but we already knew about that.
Here’s what Nvidia has to say about the fifth core:
This extra core – which we call the “companion core” – runs at a lower frequency and operates at exceptionally low power.
During less power-hungry tasks like web reading, music playback and video playback, Kal-El completely powers down its four performance-tuned cores and instead uses its fifth companion core. For higher performance tasks, Kal-El disables its companion core and turns on its four performance cores, one at a time, as the work load increases.
The Variable SMP architecture is also completely OS transparent, which means that operating systems and applications don’t need to be redesigned to take advantage of the fifth core.
That sounds great ! It should mean more battery life and the source code of the OS and/or applications does not need to be modified to take advantage of this core. I did not know video playback was a low power operation before this post… I guess it’s because now most of it is handled by hardware.
vSMP (Variable Symmetric Multiprocessing) is a new technology developed by Nvidia used in Kal-El processor. The companion core is also an ARM Cortex A9 (like the 4 other cores) but apparently built using a special low power silicon process. This core uses less power at low frequencies, but more power than other cores at higher frequencies (See chart below) and its frequency will be limited to 500 Mhz.
That means that device using Nvidia Tegra 3 will consume much less than other products when it is in standby mode with possibly a standby time of several months. For comparison, the Samsung Galaxy Tab built around the Nvidia Tegra 2 has a standby time of 650 Hours (~27 days). It will also greatly improve the performance when only background tasks are running or when you are simply listening to music on your phone.
All 5 cores will not run at the same time: It’s either the companion core by itself for low power operations (background tasks, audio, video, email syncs, social media syncs, etc..), one core, two cores or four cores for more demanding operations.
For more details on the “low power companion core”, you can read “Variable SMP A Multi-Core CPU Architecture for Low Power and High Performance“.