An article in an IBM research publication by Dharmendra S. Modha describes the most recent progress of a team of researchers who have been busy over the last ten years designing a processor which better models the functioning of a human brain.
The brain’s cerebral cortex is thought to be made up of repeating canonical cortical microcircuits. Using this model the team were able to design and demonstrate in 2011 an event-driven “worm-scale” neurosynaptic core chip that integrated computation and memory. Now in their latest development they have managed to shrink the neurosynaptic core by 15-fold in area and 100-fold in power, and have tiled 4,096 cores via an on-chip network to create the TrueNorth chip. This is fabricated in Samsung’s 28nm process and uses 5.4 billion transistors making it IBM’s largest chip to date in transistor count. While simulating complex recurrent neural networks, TrueNorth consumes < 100 mW of power and has a power density of 20 mW / cm2.
Unlike the usual von Neumann architecture which relies on sequential fetch-execute cycles TrueNorth has a parallel, distributed, modular, scalable, fault-tolerant, flexible architecture that integrates computation, communication and memory. It does not use a common clock but instead has an event-driven digital mixed synchronous-asynchronous neuromorphic architecture. This reduces neuron switching by 99% on average for a typical network. The resulting power consumption is typically 70 mW and specific power consumption is 46 bn synaptic operation/s/W. According to Modha “We foresee generations of information technology systems that complement today’s von Neumann machines powered by an evolving ecosystem of systems, software, and services, these brain-inspired chips could transform mobility, via sensory and intelligent applications that can fit in the palm of your hand without the need for Wi-Fi.”
The work is part of a programme called SyNAPSE (systems of neuromorphic adaptive plastic scalable electronics) funded by DARPA, the US Defense Advanced Research Projects Agency.